Court Cases;

OLR Research Report

November 9, 2000





By: James J. Fazzalaro, Principal Research Analyst

You asked for a review of the use of field sobriety tests for drunk driving enforcement and, specifically, the so-called “California tests.” You wanted to know the scientific basis used for giving the field sobriety test battery, how it is determined if someone passes or fails the tests, and what Connecticut cases allow this information to be used to remove a license.


Until the mid 1970s, police departments around the country used many different types of field sobriety tests in enforcing drunk driving laws. There was little consistency or standardization in the tests being used. Concerned over this lack of consistency, the National Highway Traffic Safety Administration (NHTSA) initiated an effort to identify the best tests for enforcement use and standardize the way they were administered and scored. NHTSA sponsored a 1977 study in which researcher were asked to identify the tests being used throughout the country and recommend a “best” test battery for further development. Out of the dozens of different tests then in use, the researchers identified three—the walk-and-turn, one-leg-stand, and horizontal gaze nystagmus tests—as the most accurate, practical, and reliable tests for enforcement purposes. A subsequent 1981 study developed a standardized set of administration and scoring principles intended to promote consistency in the use of these tests. These three tests are now known as the Standardized Field Sobriety Test Battery and form the basis of a NHTSA training program for police officers.

The test battery is currently used in all states, but there are no mandatory requirements for use and many other field sobriety tests also remain in use. However, NHTSA maintains that only the three-test battery has been validated for accuracy and endorses no other tests as equally reliable.

The NHTSA training protocol requires police officers to follow the designated administration and scoring rules exactly or else the accuracy and validity of the tests are compromised. While the tests have wide acceptance in the drunk driving enforcement community, attorneys who specialize in drink driving cases, a number of researchers, and others have raised numerous issues and identified significant problems with both the scientific underpinnings and administration of field sobriety tests. One of the most significant of these criticisms is the assertion that while the field tests have been developed solely for the purpose of assisting police officers in making drunk driving probable cause determinations in the field and are not capable of determining actual impairment, the courts frequently accept them as evidence for exactly the opposite reason for which they were created.

NHTSA accepts and endorses only its standardized three-test battery and discourages reliance on other nonvalidated field sobriety tests. The use of field sobriety tests is usually the last of three phases of information gathering in which police officers engage prior to making a drunk driving arrest decision. The first two phases of the pre-arrest process involve the observations officers make and the conclusions they draw while observing vehicle operation prior to stopping it and while interacting with the driver before he exits the vehicle. Observations made during all three contribute to the officer's determination of probable cause for arrest and have relevance in court.

In the NHTSA standardized test battery, each of the three tests is administered and scored separately. Each test has a specific number of scoring points or “clues” that determine how the suspect should be classified. If the suspect exhibits a designated number of these clues in a particular test, the NHTSA guidelines say that the person can be classified as likely to have a blood alcohol level above the .10% limit of most state drunk driving laws. For example, if a suspect exhibits two of eight possible scoring clues on the walk-and-turn test, the NHTSA guidelines state that there is a 68% probability that the person's blood alcohol level is above .10%. The probabilities for the other two tests detecting someone with illegal intoxication levels based on the scoring criteria are 65% for the one-leg-stand test and 77% for the horizontal gaze nystagmus test. NHTSA maintains that the identification probability for the walk-and-turn and nystagmus test combined is 80%.

Other than the horizontal gaze nystagmus test, field sobriety tests have generally been treated by Connecticut courts as nonscientific evidence that can be submitted to the jury for consideration as observations of a defendant's balance, coordination, and ability to follow directions to which it could apply its common knowledge. In 1995, the appellate court ruled that the horizontal gaze nystagmus test was, in fact, scientific evidence that required special foundation before being admissible (State v. Merritt). This concept was further developed in a 1998 decision (State v. Carlson). We found no case decisions that purport to deny the admissibility of evidence stemming from administration of other types of field sobriety tests and they appear to be generally acceptable in court as part of a fabric of observations a police officer makes that juries are deemed capable of weighing within their common knowledge. A 1998 decision (State v. Gracia) specifically rejected the contention that field sobriety tests other than the horizontal gaze nystagmus test should be considered scientific evidence subject to special conditions for admission.


The “scientific” basis on which rests most of the credibility for use of field sobriety tests in drunk driving enforcement consists mainly of two NHTSA-sponsored studies conducted in 1977 and 1981, and several follow up research projects intended to validate the tests using data gathered in the field.

Initial Field Sobriety Test Research (1977)

Until approximately the mid-1970s, there was very little consistency among police department practices in selecting and administering field tests they used during drunk driving enforcement. Different police agencies used different tests and administered and interpreted them differently. The Los Angeles Police Department was among the first to use field tests in the enforcement and arrest process so they generally became known as the “California” tests in the law enforcement community. Because of the inconsistencies exhibited in the selection and administration of field sobriety tests and the existence of little or no scientific evidence of their validity or effectiveness, NHTSA began to take an interest in identifying the best tests police officers could use at the roadside. In 1977, NHTSA awarded a contract to three researchers at the Southern California Research Institute in Los Angeles, California to study the problem of police identification of drunk or alcohol-impaired drivers. The study contract ran until March 1981.

The grant required the researchers to examine the various field sobriety tests then in use throughout the country and determine a clinical relationship between the performed test and alcohol impairment. They had to establish a direct link between alcohol impairment and the specific test failure.

Beginning in 1975, the researchers rode with police officers in a number of states and from the many types of field tests being conducted they developed a list of about 16 tests they felt were feasible as potential sobriety tests. Following a small group pilot test of all the tests, the researchers narrowed the list to six tests that would be the subject of the 1977 NHTSA study, along with four alternate tests. The selected tests were evaluated in laboratory experiments using 238 test subjects and 10 police officers who evaluated the subjects using the tests and had to decide whether they should be arrested or released had the tests been performed at roadside, assuming a legal threshold of .10% BAC as the basis for arrest.

The 1977 study had three stated objectives:

1. To evaluate currently used physical coordination tests to determine their relationship to intoxication and impairment

2. To develop more sensitive tests that would provide more reliable evidence of impairment, and

3. To standardize the tests and observations and thus given police more consistent evidence for use in court.

(M. Burns & H. Moskowitz, Psychophysical Tests for DWI Arrest, DOT-HS-5-01242, January 1977)

The six selected tests evaluated in the study are explained below.

● One Leg Stand—The subject must stand with heels together with arms at his sides, raise one leg about 6 inches off the ground, and hold that position for 30 seconds without swaying, using his arms for balance, or putting the foot down.

● Walk-and-Turn—The subject must walk nine steps heel-to-toe in a straight line, turn by pivoting on his left foot, and walk nine heel-to-toe steps back without swaying, stopping, stumbling, using his arms for balance, taking too few or too many steps, or walking in other than a straight line.

● Finger-to-Nose—The subject must stand erect with closed eyes, head tipped back, and hands extended horizontally. He then must touch the tip of the index finger to the tip of the nose, using both the left and right hand as the officer instructs.

● Finger Count—The subject must touch and count each finger in succession counting “1-2-3-4-5, 5-4-3-2-1” out loud.

● Horizontal Gaze Nystagmus (HGN)—The subject must follow the movement of a small light or object without moving his head. The officer looks for jerking of the eyes or “nystagmus” when the moving object is at an angle of 45 degrees or less. Besides determining the angle at which nystagmus begins, the officer also must observe and evaluate any breakdown in smooth eye pursuit of the target and the distinctiveness of the nystagmus at the point at which the eye has moved as far to the side as it will go.

● Finger Tracing—The subject traces a defined figure with his finger and the police officer observes any deviation.

The alternate tests that also were examined in the 1977 study included the Romberg Balance (feet together, arms at sides, eyes closed, and head tilted backwards while the officer observes for body sway), subtraction, counting backward, and letter cancellation tests.

Subjects were all alcohol consumers and were instructed not to eat for four hours prior to the experiments. They were given measured doses of alcohol such that they would have BACs ranging from 0 to .15%, but the tests subjects did not know the amount of the dose each received. Officers had to administer the test package and determine if the person should likely be arrested for having a BAC at or above .10%.

The researchers in the 1977 study concluded that all of the field sobriety tests examined were “alcohol sensitive,” but that the walk-and-turn, one-leg-stand, and horizontal gaze nystagmus tests were the most effective at correlating with BACs of .10% or more. They considered these the best tests for further development and validation.

Some of the most significant conclusions the researchers drew are summarized below.

● While all of the tests examined were found to be “alcohol sensitive”, that is, performance was affected by alcohol consumption to some degree, they were not all equally accurate.

● The arrest/release decisions made by the police officers were correct for 74% of the test participants with the high rate of false arrest decisions due, in the researchers opinions to the officers adopting a lower level of impairment as a decision criterion than would typically be applied in the field.

● An alternate method of interpreting the subjects' test results using a linear regression statistical technique yielded an 83% correct classification figure.

● The one-leg-stand, walk-and-turn, and HGN tests were considered to be the most accurate and reliable and were recommended for further evaluation as a standardized test battery.

● The HGN test was the most reliable of the three tests with a correlation coefficient of 0.68, compared to 0.55 for the walk-and-turn test and 0.48 for the one-leg-stand test. The combined correlation coefficient for the three-test battery was 0.702. (In effect, the higher this number is within a range of 0 to 1.0, the more the test elements correlated with identifying subjects with the target BAC of .10% or more).

● If balance and walking skills are examined and the eyes are checked for the jerking nystagmus movement, the officer will have as much information about intoxication level as can be obtained at roadside.

Developing the Standardized Sobriety Field Test Battery (1981)

NHTSA subsequently awarded the Southern California Research Institute researchers a second contract to evaluate only the walk-and-turn, one-leg-stand, and HGN tests as a standardized test battery. The study objectives were to: (1) standardize the administration and scoring procedures for the three-test battery; (2) determine the reliability and validity of the standardized test battery in the laboratory; and (3) assess its feasibility, utility, and validity in the field. (V. Tharp, M. Burns & H. Moskowitz, Development and Field Test of Psychophysical Tests for DWI Arrest, DOT-HS-8-01970, March 1981).

The 1981 study essentially followed the same laboratory test procedure as the 1977 study except that it was limited entirely to these three tests. There were 297 test subjects who were given alcohol doses resulting in BAC levels of 0 to .18%. The researchers standardized the administration guidelines, test instructions, test demonstrations, and scoring criteria with 25 pilot test subjects.

The researchers reported that, on average, the police officers' estimates of the BACs of the people they tested differed by .03% from their actual measured BACs. The officers were able to classify 81% of the test subjects with respect to whether their BACs were above or below the .10% level.

The researchers also conducted a limited three-month field evaluation which resulted in incomplete data to reach any conclusions, but the researchers felt that trends in the field test suggested “positive results will be obtained if the test battery is widely used.” They concluded that no further research was necessary to standardize the tests but a more comprehensive field evaluation was necessary and future research should take into account police attitude and motivation, an adequate timeframe for data collection, and numerous issues involved in obtaining law enforcement cooperation for such an effort.

Validating the SFST Battery (1995)

Although there have been several studies attempting to validate the SFST battery under field conditions, the one that is most frequently cited in the literature by those on both sides of the drunk driving enforcement issue is the 1995 Colorado validation study. Funded by NHTSA, the study was conducted for the Colorado Department of Transportation and, once again, the principal researcher was Dr. Marcelline Burns of the Southern California Research Institute. In her introduction to the final report, Dr. Burns makes two notable observations about the previous research that developed the SFTB. First, she notes that it “is clearly relevant” to ask if the methods used in the experiments were scientifically sound, but it should be recognized that the results “are now only indirectly enlightening about current roadside use of the tests.” She notes further that controlled laboratory conditions are less variable and therefore “may be less challenging” than the highly varied conditions usually encountered in the field.

Dr. Burns second point about her prior research is that police officer experience with the SFSB is “key to the skill and confidence with which they use them as a basis for their decisions.” She observes that the officers who participated in the 1977 and 1981 studies had not been trained in administering and scoring the tests until just before the experiments. Thus they had no time or opportunity to gain skill and confidence in the tests. Since a number of years have passed with police officers gaining experience in using the test battery, she believes it is reasonable to “expect that their decisions based on use of the tests would be more accurate that the officers used in the original research.” (M. Burns, A Colorado Validation Study of the Standardized Field Sobriety Test (SFST) Battery, Final Report Submitted to the Colorado Department of Transportation, November 1995, p.1).

She identified the essential question to be examined in the study to be “How accurate are the arrest decisions which are made by experienced, skilled officers under roadside conditions when they rely on SFSTs?” She noted that a broadly applicable answer to this question could not be found in laboratory research and, instead, required field data that provides information about real world arrest decisions made by officers trained under the NHTSA guidelines for administering the test battery.

Volunteers from seven Colorado police agencies submitted records from every administration of the SFST battery over a five-month period. This produced 305 records for evaluation. A significant majority of the records produced for the study were provided in the first two month of the five-month period. The evaluation ultimately considered the correctness of only 234 of the 305 records since only cases for which a BAC was determined by a breath or blood specimen were considered. A subject's BAC was unknown if he was released when no observer was present, or if an arrested driver refused to provide a specimen (p.11). Dr. Burns notes that breath specimens were obtained “either with instruments approved for evidential tests or with PBTs at roadside (p.13). (PBTs are preliminary breath test devices which are used prior to arrest in some states, but are criticized by some as not reliably accurate.)

The study concluded that for the 234 subjects who provided BAC samples, the police officers decisions to arrest or release were correct in 86% of the cases. Decisions to arrest were correct in 93% of the sample used and decisions to release were correct in 64% of the sample. (It should be noted that the Colorado study included BACs down to .05% in the arrest category since Colorado law at the time defined impaired driving as a BAC of .05% to .099%.)

Criticisms of the Field Sobriety Test Research

Manuals for defense attorneys raise a number of points regarding alleged weaknesses in the research supporting field sobriety tests generally and the SFST battery specifically. These manuals also assert that many subjective factors may intrude on objective administration of the field tests. The manuals cite NHTSA statements in its training documents to the effect that deviation from the standardized procedures for administering and scoring the tests detrimentally affects their accuracy. Among the other factors the manuals identify include the physical conditions of the testing environment, the particular characteristics of the individual, the pressures placed on the individual, the unusual nature of the tests themselves, and the possibility of a police officer's individual predisposition towards arrest affecting his interpretation of driver behavior (Richard Erwin, Defense of Drunk Driving Cases, Chapter 10; Lawrence Taylor, Drunk Driving Defense, Fifth Ed., Chapter 4; John O'Brien, Defending DWI Cases in Connecticut, Second Edition, Section B; Phillip Price, Jr., Field Sobriety Testing, Instructional Material, National College for DUI Defense, Harvard University, July 1996). Other significant research criticizes the SFTB research and attacks their use at trail as a basis for probable cause (Nowaczyk & Cole, Separating Myth from Fact: A Review of Research on Field Sobriety Tests, Champion, Aug. 1995; Simpson, Attacking NHTSA's Three-Test Field Sobriety Assessment, 5 DWI J.: L & Sci 9, 1988; Compton, Pilot Test of Selected DWI Detection Procedures for Use in Sobriety Checkpoints, DOT-HS-806-724)).

Erwin discusses these perceived weaknesses in the research at length in his treatise and some of his major criticisms are briefly summarized below. One of Erwin's major points with respect to the use of field sobriety tests is the apparent contradiction between what they were developed for and how they are admitted by many courts. He states that the primary purpose for developing the SFST battery was to assist the police officer in making an arrest decision. The tests were correlated with their ability to determine whether a subject's BAC was at least .10% or below .10%. They were not correlated directly with driving impairment nor are they capable of determining if a person's driving ability is actually impaired. To a significant degree, neither the researchers who have conducted most of the seminal research on field sobriety tests or NHTSA itself appear to disagree substantively with this assessment. A recent report on validation of the SFST battery at BACs below .10% states,

“Driving a motor vehicle is a very complex activity that involves a wide variety of tasks and operator capabilities. It is unlikely that complex human performance, such as that required to safely drive an automobile, can be measured at roadside. The constraints imposed by roadside testing conditions were recognized by the developers of NHTSA's SFST battery. As a consequence, they pursued the development of tests that would provide statistically valid and reliable indications of a driver's BAC rather than indications of driving impairment. The link between BAC and driving impairment is a separate issue, involving entirely different research methods. …” (J. Stuster & M. Burns, Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent, Anacapa Sciences, Inc. NHTSA, August 1998, p. 28.)

Erwin states that courts have usually admitted field sobriety test results as evidence of impairment, but not as evidence of a specific BAC, and usually not even as evidence of whether someone's BAC is above a certain level. This, he feels, leads to the apparent contradiction that the courts will not accept the SFST battery for the purpose for which they were developed and the method by which they were validated, but will accept them for purposes for which they have not been directly studied or validated (Erwin, Defense of Drunk Driving Cases, Sec. 10.09(6)).

Some of the other major criticisms in the literature are summarized below. We have presented them as propounded by the critics, but note that counterpoints to these assertions have been made in the literature as well.

● The 1977 study indicates that 47% of the subjects who would have been arrested based on the test battery had BACs less than .10% and that this false positive rate only decreased slightly to 32% in the subsequent 1981 study. Erwin implies that either of these percentages is unacceptably high. He cites a suggestion advanced in by Nowaczyk and Cole that this improvement may have been a bias introduced in the latter study when fewer test subjects were selected to have BACs near the critical .10% level (22% in the 1981 study compared to almost 33% in the 1977 study) coupled with the easier task of identifying subjects with much higher or much lower BACs (Erwin, Sec. 10-09(6) citing Nowaczyk & Cole, Separating Myth From Fact: A Review of Research on the Field Sobriety Tests, Champion, August 1995, p. 40).

● Test subjects in the original studies were not adequately screened for the presence of drugs which could have affected the behaviors the police officers were observing, particularly with respect to the mistakes made in categorizing test subjects with no or moderate BACs as arrest candidates.

● The test results did not reproduce themselves well and thus are not as scientifically reliable as the researchers claimed. Critics, such as Nowaczyk and Cole, assert that to be considered scientifically reliable, tests should show a reliability coefficient in the high .80s to .90s. (A coefficient at or close to 0 would indicate no reliability or consistency in the test results while one close to 1.0 indicates a very high degree of reliability.) They assert that the test-retest portion of the 1977 study, in which 100 of the original test subjects were brought back for retesting two weeks later by the same officers, yielded a reliability coefficient of only 0.77 which they state indicates that 23% of the variability in test results is due to scoring errors. When the same subjects were tested at the same doses by different officers, the reliability coefficient dropped to 0.57. In the 1981 study, the reliability correlations ranged from .60 to .80.

● The correlation coefficients of the three tests were not sufficiently high to establish them as scientifically valid methods for determining BACs.

● The research developing and standardizing the SFST battery does not establish a baseline level of performance for the test maneuvers that accounts for differences in age, gender, physical stature and condition, and coordination. Critics also assert that the test subject pool in the 1977 and 1981 research was too heavily dominated by males and persons between 21 and 35 years old to be considered reliable in determining what typical test performance should be in the entire population.

● Much of the significantly lower rate of false positives found in the 1995 Colorado validation study (7.4% compared to 47% in the 1977 study and 32% in the 1981 study) can be explained by the lower BAC arrest criterion of .05% that was necessary under the Colorado law than to training and experience factors associated with the participating police officers.


The enforcement process that typically leads up to a drunk driving arrest can generally be separated into three fairly distinct phases. The NHTSA, which establishes training and certification standards for training police officers in drunk driving enforcement identifies them in its training manuals as actions taken by police officers (1) while the vehicle is in motion, (2) during the initial personal contact with the presumed suspect, and (3) the pre-arrest screening process. Administration of field sobriety tests is the main component of this third phase. All three phases generally have the same objective, e.g., to provide the enforcement officer with a basis for determining whether there is probable cause to arrest the suspect for driving under the influence of alcohol.

The NHTSA manual states that each phase represents a set of actions and observations that should be used by the officer to answer three questions. These are:

1. Should I stop the vehicle?

2. Should the driver exit?

3. Is there probable cause to arrest the suspect for DWI?

(DWI Detection and Standardized Field Sobriety Testing, Student Manual, NHTSA Report No. HS 178 R10/95 (1995), Sec. IV-3, Exhibit 4-2)

The manual states that all of the information gathered in these phases is supposed to both assist the officer in the decision making process and gather and accumulate evidence in a form that can be most effectively utilized in court.

Phase I—The Vehicle in Motion

Except when drunk driving enforcement occurs through established sobriety checkpoints or at an accident scene, the first interaction with a police officer occurs when things about a particular vehicle draw the officer's attention and indicate to him that the vehicle should be stopped and investigated. Sometimes this may be unrelated to the driver's actions, such as when there is an obvious equipment defect or an expired registration or inspection sticker. But NHTSA has identified a number of visual driving cues that it recommends police officers use to associate with alcohol-impaired driving. Because this material is widely distributed to police agencies and included in the recommended NHTSA training program, it generally has become the initial basis upon which they begin to establish probable cause in drunk driving enforcement.

This material was first published in 1981 as Visual Detection of Driving While Intoxicated—An Explanation of the DWI Detection Guide (DOT-HS-805711). It listed 20 driving cues that NHTSA believe its research showed were the best ones for discriminating night-time drunk drivers (.10 BAC or more) from night-time sober drivers. The cues were based on field studies where 4,600 patrol stops were correlated with BAC measurements. NHTSA maintained that the 20 cues could be associated with 90% of all drunk driving detections. The detection guide also assigned a probability to each of the cues purporting to indicate the relative probability that a driver exhibiting the cue was driving with a BAC of .10% or more. But NHTSA cautioned that the probability values were intended primarily to emphasize the relative importance of a particular cue and did not endorse using them when testifying in court.

The probability values ranged from 65% for turning with a wide radius and straddling a center or lane marker line to 30% for driving with headlights turned off or rapidly accelerating or decelerating. Seven of the 20 cues indicated a probability of more than 50%, four indicated a 50% probability, and the remaining nine a probability of less than 50%. But NHTSA also maintained that when more than one cue was observed, the officer should add 10 to the highest probability of an observed cue. For example, observing a driver weaving within a lane or between lanes (50%) and showing too slow a response to a traffic signal (40%) should be interpreted as a 60% probability that the driver had a BAC of .10% or more. Thus the highest probability that could be inferred through these cues was 75%, but NHTSA also asserted that police could use this system for predicting BACs of .05% by adding 15 to the cue's probability value.

NHTSA reissued its visual detection guide in 1998 based on additional field studies it commissioned, ostensibly for the purpose of adapting the guide for BACs down to .08%. It added four additional cues, some of which describe behaviors that could only be observed after the vehicle has been stopped or signaled to stop, revised some of the probability percentages, and included an additional set of post-stop cues that could be used when observing the driver's behavior once the vehicle was stopped.

The new guide is slightly more difficult to interpret than the 1981 version in that it does not list the cues and their probability rating individually. Instead it groups them into four categories and specifies the range of probabilities within the category. The cue groupings are explained below.

Problems Maintaining Proper Lane Position—50%/75%

Weaving within lane, weaving across lane lines, straddling a lane line, swerving, turning with a wide radius, drifting, or almost striking a vehicle or other object.

Speed and Braking Problems—45%/70%

Stopping problems (too far, too short, or too jerky), accelerating or decelerating for no apparent reason, varying speed, or slow speed (10 mph or more under the speed limit.

Vigilance Problems—55%/65%

Driving in opposing lanes or wrong way on one-way road, slow response to traffic signals, slow or failed response to officer's signals, stopping in lane for no apparent reason, driving without headlights at night, or failure to signal a turn or lane change or signaling that is inconsistent with the action taken.

Judgment Problems—35%/90%

Following too closely, improper or unsafe lane change, illegal or improper turn (too fast, jerky, sharp, etc.), driving on other that the designated roadway, stopping inappropriately in response to officer, inappropriate or unusual behavior (throwing objects, arguing, etc.), appearing to be impaired (slouching, staring straight ahead with eyes fixed, tightly gripping the steering wheel, face close to the windshield, other indicators of appearance consistent with impairment.)

Post Stop Cues—85%

Difficulty with motor vehicle controls; difficulty exiting vehicle; fumbling with driver's license or registration; repeating questions or comments; swaying, unsteadiness, or balance problems; leaning on the vehicle or other object; slurred speech; slow response to officer or necessity for officer to repeat questions; providing incorrect information or changing answers; odor of alcohol.

The reissued detection guide explains the interrelationship of the individual cues differently. It states that if a driver is observed weaving in a lane or across lane lines, there is a 50% probability of a BAC of .08% or more, but if either weaving cue is observed with any other cue, the probability becomes 65%. Observing two cues other than weaving indicates a probability of at least 50%, although some cues such as swerving, accelerating for no apparent reason, or driving on other than the designated roadway have single-cue probabilities of more than 70%.

Phase II—Personal Interaction with the Driver

The second phase of enforcement is the police officer's face-to-face driver observations and interview and, if the process proceeds further, observations of how the driver exits the vehicle and responds to the officer's directions. Sometimes, the officer may use pre-exit tests aimed at testing the driver's divided attention function or physical condition. This phase of the enforcement process is somewhat less defined procedurally and individualized to the particular officer or department policy. Nevertheless, the general thrust of the encounter is for the officer to elicit responses from the suspect and make observations as to his appearance, demeanor, speech, and attitude that the officer can use to decide on further actions. The NHTSA student training manual states that the driver interview provides the first definite indications that the driver is under the influence (Sec. VI-2). Frequently, the officer will ask the suspect at this point if he has been drinking.

The NHTSA training manual recommends that officers ask certain types of questions that can serve as simple divided attention tests. These can be of three types, specifically: (1) asking for two things simultaneously such as a license and registration, (2) asking interrupting or distracting questions, or (3) asking unusual questions. (Sec. VI-4, -5) In the case of asking for two things simultaneously, NHTSA training procedures instruct the officer to be observant as a possible sign of intoxication if a driver fails to produce both documents; produces other than the requested documents; fails to see the documents while searching in a wallet or purse; fumbles with or drops a wallet, purse, or the requested documents; or is unable to retrieve the documents using the fingertips.

With the second technique, the officer might ask the driver to produce his license and registration and while he is doing this ask him some unrelated question such as the correct time. NHTSA training procedures instruct the officer to be alert to a driver who ignores the question and concentrates only on the initial task of retrieving the documents, forgets to resume the document search after answering the question, or supplies a grossly incorrect answer to the question.

The third technique of asking unusual questions is employed after the driver has retrieved his license and registration. For example, while holding the license the officer might ask the driver for his middle name. The manual states that if he is not expecting to have to process this information and is impaired, he may have difficulty responding to the unusual question and answer what would be a usual question he is prepared to answer, such as his first name.

The final stage in this phase, if it progresses further, is the vehicle exit sequence. During this phase, the NHTSA training manual instructs the officer to be alert for a driver who shows angry or “unusual” reactions, cannot follow instructions, cannot open the door, leaves the vehicle in gear, “climbs” out of the vehicle, leans against the vehicle, or puts his hands on the vehicle for balance VI-6).

Phase III—Pre-arrest Screening and Administration of Field Sobriety Tests

This final phase of establishing a basis of probable cause for arrest involves administration of the structured field sobriety tests. In some jurisdictions that allow for them, this can also include administration of a preliminary breath test.

As indicated earlier in this report, NHTSA has developed and promotes the use of the Standardized Field Sobriety Test battery consisting of the Walk-and-Turn (WAT), One-Leg-Stand (OLS), and Horizontal Gaze Nystagmus (HGN) tests. NHTSA recognizes only these tests in its training protocols and does not endorse the use of any other types of field sobriety tests and similarly validated. It also makes it clear that the validity of the test battery depends on strict adherence to the designated administration and scoring principles it has developed. If they are followed exactly, NHTSA asserts that the HGN test is 77% reliable in identifying those with BACs of .10% or more, the WAT test is 68% accurate, and the OLS test is 65% accurate. The HGN test combined with the WAT test is claimed to have 80% reliability. If the procedures are not followed exactly, NHTSA states that “the decision making guidelines will not be accurate.”

Failure to pass any of the three tests is determined by counting specific scoring clues NHTSA specifies for each test. Presence of a predetermined number of clues indicates failure to perform the test.

Each of the three tests in the SFST battery is briefly described below, along with the administrative steps that must be followed and the scoring clues applicable to each test. The actual descriptions in the NHTSA manual are considerable more extensive. In addition, the standardized procedures for each test generally require that the officer provide clear and specific directions and demonstrate what the subject must do. Failure to do so invalidates the test effectiveness. The tests must be administered outside the vehicle in a well-lighted area suitable for walking and standing and safe from traffic.

The Walk-and-Turn (WAT) Test

The test has two distinct parts. The first part (instruction phase) requires the subject to balance heel-to-toe while the officer gives the instructions and demonstrates the test. The second part of the test requires the subject to take nine heel-to-toe steps on a straight line, pivot around, and take nine heel-to-toe steps back.

Test Conditions. The required test conditions are level ground, a hard, dry, non-slippery surface, and conditions under which the suspect is in no danger should he fall. The student training manual states that the test criteria are not necessarily valid for people age 65 or older or people with leg injuries or inner ear disorders. (Prior editions of the manual stated this limitation as applicable to people more than 60 years of age, more than 50 pounds overweight, or with physical impairments that affect balancing ability. The reason for the change does not appear in the manual.) Suspects with heels more than two inches high must be given the chance to remove their shoes. The WAT test requires a line that the suspect can see and follow. If a natural line is not present, the officer must draw one in the dirt or on a sidewalk with chalk. Walking parallel to a curb is not acceptable. The suspect must be able to see to perform the test. His eyes must be open and adequate light available. The manual states that if the officer can see the suspect clearly the lighting is adequate, otherwise the officer must use a flashlight to illuminate the line. A person who cannot see out of one eye may have difficulty performing the test because of poor depth perception. The suspect must watch his feet because this makes the test more difficult for an intoxicated person. The officer must observe the suspect performing the test from three to four feet away and remain motionless. Standing too close or moving while the test is going on makes it more difficult even for a sober person to perform the test.

Standardized Test Procedures. The WAT test must be administered as follows.

● Instruct the subject to place the left foot on the line and the right foot heel-to-toe in front of it (demonstrate).

● Verify that the suspect understands that the stance must be maintained while the instructions are given.

● If the suspect breaks from the stance during the instructions, stop the instructions until the stance is resumed.

● Tell the suspect that he will be required to take nine heel-to-toe steps down the line, turn around, and take nine steps back down the line but not to begin until instructed.

● Demonstrate two or three heel-to-toe steps and the turn.

● Instruct the suspect to keep both arms at his sides, watch his feet, count the steps out loud, and not to stop walking until the test is completed.

● Ask if the suspect understands the directions and, if not, repeat whatever he does not understand but not the entire set of directions.

● Tell the suspect to begin and to count his first step from the heel-to-toe position as one.

● If the suspect staggers, steps off the line, or stops while walking, allow him to resume from the point of interruption. Do not have him repeat the test from the beginning. (The manual states that the test loses its sensitivity if it is repeated.)

Standardized Scoring Clues. The WAT test procedure has eight specific scoring clues the officer must track. The clues must be scored if the suspect:

Loses balance during the instructions (his feet break from the heel-to-toe stance)

Starts walking before the instructions are completed and he is instructed to start.

Stops while walking to steady himself (but do not score this clue if he is only walking slowly).

Leaves more than one-half inch between his feet during any heel-to-toe step.

Steps off the line (if this occurs three times the test is terminated and the officer must score it as if all eight clues were shown).

Raises one or both arms more than six inches from his side to maintain balance.

Turns improperly either by removing the front foot from the line while turning, removes both feet from the line, or clearly does not follow the directions as demonstrated.

Takes the wrong number of steps in either direction.

If the suspect cannot do the test, the officer must score it as if all eight clues were present.

If the suspect clearly exhibits two or more of the eight clues or cannot complete the test, the officer must classify his BAC as above .10%. Officers are instructed to note in their report how many times each clue appears, but count it only once for scoring purposes.

The One-Leg-Stand (OLS) Test

The OLS test requires a suspect to stand with his arms at his side and raise and hold one leg at least six inches off the ground for 30 seconds. He must count the seconds out loud according to specific instructions. The 30-second time period is important to the test since NHTSA research indicates that it makes the test sensitive to people in the .10% to .15% BAC range who might otherwise pass the test if they only had to maintain the position for less time. NHTSA research has shown that someone with a BAC above .10% can maintain balance for up to 25 seconds but seldom for 30 seconds.

Test Conditions. The conditions required for the OLS test are like those for the WAT test. There must be light adequate to provide a visual frame of reference. The officer must observe motionless from three to four feet away for the same reasons as for the WAT test. The test criteria are not necessarily valid for people age 65 or older, people 50 pounds or more overweight, or people with leg injuries or inner ear disorders.

Standardized Test Procedures. The NHTSA specified test procedures for the OLS test are as follows.

● Instruct subject to stand with feet together and arms down at sides (demonstrate).

● Tell subject not to start until told.

● Ask if subject understands instructions.

● Explain to the subject that when told to start he must raise one leg, either his left or right, approximately six inches off the ground with the toe pointed out (demonstrate stance).

● Tell the subject he must keep both legs straight with his arms at his side and, while holding the position count out loud for 30 seconds saying “one thousand and one, one thousand and two, etc.” until told to stop (Demonstrate the counting method).

● Remind the subject he must keep both arms at his sides at all times throughout the test and keep watching his raised foot.

● Ask if he understands and get a confirmation of his understanding.

● Tell him to begin the test.

● Observe the subject from three feet away and remain “as motionless as possible.” If he puts his foot down, instruct him to pick it up again and resume counting from the point it touched the ground. If he counts very slowly, end the test after 30 seconds. If he counts quickly, make him continue until told to stop.

Standardized Scoring Clues. The test is scored according to four scoring clues. If the suspect

● Swaying side-to-side or back-and-forth while maintaining the one-leg stance

● Moving arms six inches or more from the sides to maintain balance

● Hopping in order to maintain the one-leg stance

● Putting his foot down one or more times during the 30 seconds.

If the suspect cannot do the test or puts his foot down three or ore times, the officer must record the results as if all four clues were scored

Horizontal Gaze Nystagmus (HGN) Test

The HGN test is considered the most accurate of the three tests and NHTSA suggests that it be administered at a minimum if the suspect is unable to perform the other two tests due to age, size, or physical limitations. Some of the research on these tests suggests that when it is consistently given first in the test sequence, the reliance some police officers have on it might may have a subtle influence on his expectations and scoring of the other two tests (Anderson, Schweitz, and Snyder, Field Evaluation of a Behavioral Test Battery for DWI, DOT-HS-806-475, September 1983).

Nystagmus is involuntary jerking of the eye. Research shows that there are more than 40 types of eye nystagmus. The HGN test is designed to measure the type of nystagmus that occurs when the eyes gaze to the side. HGN will occur in any person's eyes when gazing extremely sideways, but NHTSA maintains that when a person is intoxicated there are these signs that become apparent in his eye movements: (1) the nystagmus occurs much sooner, that is, the less the persons eyes have to move before the jerking occurs; (2) if the person's eyes move as far to the side as possible, the greater the alcohol impairment, the more distinct the nystagmus will be at the extreme gaze position; and (3) an intoxicated person cannot follow a slowly moving object smoothly with his eyes. The HGN test is intended to identify and measure these three signs.

The key element of measuring HGN is correctly estimating when the eye has reached a deviation angle of 45 degrees. NHTSA maintains that when someone's BAC is above .10%, the jerking will begin before his eye has moved 45 degrees to the side. Officers trained with the NHTSA training procedure are provided a template for practicing how to estimate the 45 degree angle but they are not required to use a template when they administer the test in the field.

Test Conditions. The test requires the use of an object for the subject to follow. The NHTSA training manual says that this can be a fingertip, penlight, or pen. It must be held slightly above eye level and 12-15 inches away from the person's nose. The police officer must inquire and make note of whether or not the suspect if he is wearing contact lenses, but the lenses do not have to be removed for the test. However, a suspect wearing glasses must be made to remove them.

Standardized Test Procedure. The officer must administer the test following these procedures.

● The officer instructs the suspect that he is going to check his eyes, that he must keep his head still and follow the object only with his eyes, and that he must focus on the object until told to stop.

● The officer must hold the stimulus 12-15 inches from the suspect's nose and slightly above eye level. He must move the stimulus smoothly across the suspect's entire field of vision and check to see if the eyes are tracking together or one lags behind the other. (If the eyes do not track together, it could be a sign of a medical disorder, injury, or blindness.)

● The officer next must check to see that both pupils are the same size (if not, it could be a sign of a head injury).

● The officer starts with the left eye and smoothly moves the stimulus to the right at a speed such that it takes about two seconds to being the person's eye as far to the side as it can go. He then moves the stimulus similarly to the left to check the person's right eye.

● Using this process, the officer must check for all three clues in both eyes, always starting with the left. He must check at least twice for each clue in each eye.

● The officer must check for the clues in this sequence: lack of smooth pursuit, nystagmus at maximum deviation, and onset of nytagmus prior to 45 degrees.

● When checking for nystagmus at maximum deviation, the officer must move the stimulus to the side until no white is showing at the side of the suspect's eye and hold the position for four seconds.

● When checking for nystagmus onset angle, the officer must move the stimulus at a speed that would take about four seconds to reach the edge of the suspect's shoulder. Watch the eye for jerking and, when it occurs, stop and verify that is continues.

● The four-second speed of the stimulus movement is important. If the object moves too fast, the officer could go past the point of onset or miss it altogether.

● If the suspect's eyes start to jerk before 45 degrees, the officer must check to see that some white is still showing on the side of the eye closest to the ear. If no white shows, this means either that the officer has taken the eye too far to the side (more than 45 degrees) or the person has unusual eyes that do not deviate very far.

Standardized Clues. There are three scoring clues that are measured for each eye, giving a maximum of six scoring points should all three clues be present in both eyes. If four or more clues are observed, the NHTSA manual states the person should be classified with a BAC above .10%. The are the scoring clues.

● Lack of smooth pursuit (the eyes bounce or jerk as they follow the object)

● Distinct nystagmus at maximum deviation when held for four seconds. While some people exhibit jerking at maximum deviation even when sober, in an intoxicated person the jerking should be “very pronounced, and easily observable.”

● Onset of nystagmus before the eye has moved 45 degrees.

These are the only three clues NHTSA recognizes as valid indicators of HGN. NHTSA specifically does not support the position that the exact onset angle can be used to estimate a person's specific BAC and considers this to be a misuse of the HNG test.

Combined HGN and WAT Test Scoring Matrix

NHTSA provides a special scoring matrix for officers to use when combining the results of the HGN and WAT tests. It notes that the HGN test requires four clues for classification as above .10% BAC while the WAT requires only two. The matrix can be used when the suspect scores higher on one test and lower on the other. For example, if the suspect scores three clues on the HGN test but only two clues on the WAT test, the matrix indicates that he should be classified as being above .10% BAC. But if he scores three clues on the HGN test and only one on the WAT test, the matrix shows that his BAC is probably below .10% BAC. The NHTSA manual does not link the OLS test with any other test for combined scoring purposes.


State of Florida v. Meador

We are providing information on this 1996 case from Florida because it is prominent in the literature on field sobriety testing as one of the most significant recent cases addressing the issue of how field sobriety tests are viewed in the courts. It is of particular significance because two of the leading recognized experts in the field with opposing points of view were called to testify as expert witnesses. The state used Dr. Marcelline Burns as its expert and the respondent used Dr. Spurgeon Cole as its expert. Dr. Burns is the researcher from the Southern California Research Institute who conducted the 1977 and 1981 NHTSA studies establishing and standardizing the SFST battery and participated in numerous subsequent studies to support its validity and accuracy. Dr. Cole is a clinical psychologist and professor at Clemson University who has co-authored several critical analytical reviews of field sobriety tests and the research supporting them as noted in the discussion above. The general interest in this case stems from the occasion for the court to concurrently review the testimony of two of the most recognized experts on field sobriety testing.

State v. Meador (674 So.2d 826, 1996) involves an appeal by the state of a county trial court's pretrial order excluding the evidence of a field sobriety test battery that included the tests in the NHTSA SFST battery and some other tests not in the standardized battery. The Fourth District Court of Appeal exercised it its discretionary jurisdiction to review the issue to the “disparate approaches and conclusions” of county court judges within the district with respect to admissibility of the tests.

The case involved challenges by two defendants arrested for driving under the influence in different Florida towns. Both defendants had challenged the admissibility of the field sobriety test administered to them on the grounds that they lacked both scientific reliability and probative value.

In State v. Meador, the court noted that no Florida appellate court had yet ruled directly on the admissibility of field sobriety test results, but that in 1995 the Florida Supreme Court has ruled in State v. Taylor that a pre-arrest request made to a defendant to perform field sobriety tests after an investigative stop upon reasonable suspicion of DUI was reasonable (674 So. 2d 830).

In rendering its decision the court separated the HGN test from the other tests administered to test psychomotor functions. (The psychomotor tests administered to the defendants included the walk-and-turn, one-leg-stand, Romberg balance, and finger-to-nose tests. The court determined that testimony concerning performance on psychomotor field sobriety tests is sufficiently reliable as lay observations of intoxication to be relevant in proving impairment and the danger that they be unfairly prejudicial did not substantially outweigh their probative value so as to require exclusion as evidence. It considered them admissible as lay observations of the police officer with the proviso that characterization of the test results by witnesses be restricted so as to not elevate the significance of the test result evidence above other lay observations of intoxication. Specifically, the court cautioned that caution should be exercised to restrict use of terms such as “test,” “pass,” “fail,” or “points” when referring to the results.

The court viewed the HGN test in a different light. It determined that HGN test results should not be admitted as lay observations of intoxication because HGN testing constitutes scientific evidence. Thus, although the evidence may be relevant, the court felt that the danger of unfair prejudice, confusion of issues, or misleading the jury requires exclusion of the HGN test evidence unless the “traditional predicates of scientific evidence are satisfied.” (Meador, p. 836).

Connecticut Case Decisions

State v. Lamme (216 Conn. 172, August 1990)

The defendant in this case challenged the admissibility of the results of two field sobriety tests administered to him after he was stopped for driving without lighted headlights at night. Previous to being stopped by the police officer, the defendant had been interviewed by a different police officer called by hotel management to the hotel where the defendant had consumed several drinks and fallen asleep in the lobby. The officer noticed the odor of alcohol on the defendant and when the defendant rejected an offer for arrangement of a ride home and said he would wait in his car for a friend to drive him home. When he observed the defendant walk to his car unsteadily, the officer radioed headquarters with a description of the defendant and his car. The second officer who subsequently stopped the individual heard the broadcast and drove to the vicinity of the hotel where he saw the defendant driving a car matching the description without the headlight illuminated.

The officer administered two field sobriety tests to the defendant—a walk-and-turn test and a finger-to-nose test. While the case decision provides no further description of the content of the tests, it is clear that it did not constitute the SFST battery. The decision states that “the defendant's failure to pass these tests was the basis for his arrest for driving while under the influence of intoxicating liquor.” (p. 177)

Both the trial court and the Appellate Court had concluded earlier that the defendant was not entitled to suppress the evidence of the two field sobriety tests. The courts agreed that the police had legally stopped him initially for driving without headlights and, subsequently, the odor of alcohol on his breath provided a “reasonable and articulable suspicion” that he might be involved in criminal activity and justified further detention for the “limited intrusion” represented by the field sobriety tests at the place where he was being detained. The Supreme Court agreed that this constituted a valid stop under the requirements of the U.S. Supreme Court's decision in Terry v. Ohio (392 U.S. 1, 20-22, 88S. Ct. 1868).

In his appeal to the Supreme Court, the defendant asserted that article first, nine of the Connecticut Constitution forbids the police to detain anyone, even on reasonable and articulable suspicion, unless and until the police have probable cause to make an arrest. This argument would require the court to rule the field sobriety test results inadmissible since the police had conceded that they did not have probable cause to arrest him until after administering the field sobriety tests.

The Supreme Court rejected this argument and concluded that “the principles of fundamental fairness that are the hallmark of due process permit brief investigatory detention, even in the absence of probable cause, if the police have a reasonable and articulable suspicion that a person has committed or is about to commit a crime.” (p.184). Thus the court concluded that the principles underlying constitutionally permissible stops enunciated by the U.S. Supreme Court in its Terry decision and subsequent relevant cases define when detentions are “clearly warranted by law” under article first, nine of the state constitution.

State v. Merritt (36 Conn. App. 76)

This decision appears to be the first instance a Connecticut appellate court addressed the issue of whether the HGN test and its results are the type of scientific evidence requiring a special foundation for admission. The defendant was initially stopped by police after failing to stop for a stop sign and almost colliding with the car of the arresting officer. The officer suspected the defendant to be intoxicated based on his observation that the defendant's breath smelled of alcohol, his eyes were bloodshot, his clothes disheveled, he swayed back and forth, and he spoke slowly. The police officer conducted three field sobriety tests—alphabet recitation, a ten-step walk-and-turn test, and a one-leg-stand test. Although it is not clear from the case decision if the one-leg-stand test was performed in accordance with the procedures outlined in the SFST battery, the other two tests clearly were not part of the battery.

After concluding that the defendant had failed all three of the psychomotor tests, the police officer performed the HGN test in which he made “three separate observations” of the reactions of each of his eyes. On the basis of all his observations, including those from the HGN test, he took the defendant into custody, but, for several reasons, an evidentiary breath test could not be administered.

At trial, the defendant apparently objected to the admissibility of the results of the HGN test, but not to the admissibility of the other field sobriety tests that were administered. On appeal to the appellate court, the defendant challenged the admissibility of the HGN test results as constituting scientific evidence requiring foundation according to the Frye test of general acceptability within the scientific community. The appellate court noted that no similar court had yet ruled on whether the HGN test constituted scientific evidence requiring special foundation for admission.

After reviewing the plethora of cases on this subject from other jurisdictions, the court determined that the HGN test constituted such scientific evidence and since the state had not laid the foundation for evidence pursuant to the Frye standard, it ruled that the trial court has exceeded its discretion by admitting the HGN test results. However, the court also found that this constituted harmless error and upheld the lower court's conviction based on the conclusion that the jury's perceptions of all of the other evidence, including the defendant's admission of consumption of four drinks, his failure to pass the three other field sobriety tests, and his appearance and demeanor, was not so affected by the improperly admitted testimony on the HGN test that the likely trial result would have been different without the HGN testimony.

State v. Carlson (702 A. 2d 886, 45 Conn. Sup. 461 (1998))

This case further established the specific basis for accepting the HGN test as valid scientific evidence. The court ruled that for purposes of determining if the HGN test had gained general acceptance in the particular field in which it belonged (the essence of the Frye test for acceptability), the relevant scientific communities included optometry, neurology, behavioral psychology, highway safety, and forensic science. The court further found that the test was admissibility as scientific evidence since it was generally accepted in these relevant scientific communities as a reliable indicator of alcohol impairment, it had been the subject of extensive field and laboratory testing and scholarly reivew, national standards existed to guide police officers in executing the test, and it was sufficiently straightforward that a fact finder could reasonably and realistically draw its own conclusions from it. However, the court also reinforced the position that the fact that the HGN test satisfied the standards for admissibility as scientific evidence did not obviate the necessity of laying a proper foundation with a showing that the officer administering the test had the necessary qualifications and followed the appropriate procedures.

State v. Gracia (719 A. 2d 1196, 51 Conn. App. 4 (November 1998))

This case considered several points of law relative to drunk driving issues, but it appears significant with respect the issue of field sobriety test in that it appears to be the first Supreme Court decision specifically to rule on the admissibility of field sobriety tests other than the HGN test as scientific evidence The facts of the case involved a situation where a passing motorist encountered the defendant's vehicle in the left traffic lane of a local street with the engine running, the lights on, the right turn signal flashing, and the radio playing. He observed the defendant asleep in the vehicle and tried to waken him. When he could not do so, he left to call the police and, when he returned, observed the vehicle and defendant in the same positions as when he left. He made other observations consistent with the idea that the vehicle was running and in gear with the defendant asleep behind the wheel.

When a police officer arrived, he attempted to waken the sleeping defendant for approximately five minutes before succeeding. The police officer testified that the defendant's eyes appeared glassy and bloodshot and that he detected the odor of alcohol. Following several other interactions, the officer asked the defendant to exit the vehicle and, following several additional observations relating to the defendant's condition and demeanor, the officer administered two field sobriety tests, which the decision identified as the one-leg-stand and the walk-and-turn tests.

The defendant raised a number of issues on appeal, one of which was that the judiciary was precluded from exercising jurisdiction in this case because the trial court's suspension of his license violated the separation of powers provision of the Connecticut Constitution. Among the issues raised was that the trial court improperly admitted evidence concerning the field sobriety test he was given in that these tests constitute scientific evidence requiring expert testimony prior to admission.

Before addressing this issue, the court noted that the defendant's claim that Miranda warnings were required before admisintration of field sobriety tests was unfounded because the U.S. Supreme Court had ruled in Pennsylvania v. Bruder (488 U.S. 9, 109 S. Ct. 205) that questioning at the scene and conducting field sobriety tests does not involve custody for Miranda purposes. The court further noted that its previous ruling in the Lamme case considered such testing “incident to the initial stop, based on the officer's reasonable suspicion, rather than on the subsequent arrest.”

The court rejected the argument. It ruled that the Frye test for admissibility of scientific evidence did not apply to the field sobriety test administered in this case. It found that the two administered tests assessed the defendant's balance, coordination, and ability to follow directions and that they were neither highly technical nor required special skills or knowledge in order to be understood. The court referred to its previous decision in Merritt in which it noted that these types of tests, unlike the HGN test, were within the common knowledge of lay jurors. It also noted that the trial court instructed the jury that the tests were not scientific evidence and that it should consider the observations made during the tests and use its common experience in determining whether the defendant was intoxicated.

State v. Porter (241 Conn. 57, 698 A. 2d. 739 (1997))

While not specific to field sobriety tests, this decision adopted a new standard with respect to the basis for admitting scientific evidence. It replaced the Frye standard of general acceptance within the relevant scientific community with the standard elucidated in the U.S. Supreme Court's 1993 decision in Daubert v. Merrill Dow Pharmaceuticals. Instead of “general acceptance” within the relevant community, the new federal standard established in Daubert requires only that the reasoning or methodology underlying the scientific theory or technique is scientifically valid and can properly be applied to the facts at issue. “In other words,' the court stated, “before it can be admitted, the trial judge must find that the proffered evidence is both reliable and relevant.'” (Porter p. 64)

In Daubert, the court listed four nonexclusive factors for federal judges to consider in determining whether a particular theory or technique is based on scientific knowledge: (1) whether it can be, or has been, tested; (2) whether it has been subjected to peer review and publication; (3) the known or potential rate of error, including the existence and maintenance of standards controlling its operation; and (4) whether it is, in fact, generally accepted in the relevant scientific community. However, the court also noted that the process was a “flexible” one and that other factors may have merit to the extent that they focus on the reliability of evidence as ensured by the scientific validity of its underlying principles.

In adopting the Daubert criteria as a replacement for the Frye standard, the court further acknowledged the U.S. Supreme Court's recognition that even if a scientific theory or technique satisfied both the reliability and relevance criteria of Daubert, it could still be excluded under federal evidentiary rules if its probative value was substantially outweighed by the danger of unfair prejudice, confusion of issues, or misleading the jury.