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Standardized Field Sobriety Testing

Standardized Field Sobriety Tests were developed as the result of research conducted in the mid 1970s for the National Highway Traffic Safety Administration ("NHTSA"). The purpose of this research was to develop standardized tests which would provide a reliable method of determining intoxication from field sobriety tests.

The NHTSA has concluded that three tests, if systematically conducted according to strict guidelines, can predict whether a person may be under the influence of drugs or alcohol. The only three field sobriety tests approved by the NHTSA are the Horizontal Gaze Nystagmus ("HGN") test, the Walk-and-Turn test the One-Leg Stand test.

Police officers are theoretically trained to look for established "scoring factors" or "clues" which must be evaluated in determining whether or not intoxication exists. A finding of intoxication can only arise once a certain number of clues are identified. If less then the certain level of clues are identified, the officer should conclude that there a high degree of probability of non-intoxication.

For cases that proceed to trial, it is important for defense counsel to carefully question police officers with respect to their field sobriety test training and adherence to NHTSA protocols. If a police officer is unsure of these protocols and/or the NHTSA-approved indicator system, his or her conclusions can lose credibility with a judge or jury.

1. Horizontal Gaze Nystagmus ("HGN") Test

Horizontal gaze nystagmus is an involuntary jerking of the eyeball which occurs naturally as the eyes rotate in the socket. In theory, a sober person can visually follow a moving object smoothly and without the eyeball "stopping and starting". With a person is impaired by alcohol, nystagmus is exaggerated resulting in a jerking motion as the eyes rotate. In the HGN test, the officer observes a person's eyes as the eyes follow a slowly moving object such as a pen or small flashlight. The examiner looks for three indicators of impairment in each eye: if the eye cannot follow a moving object smoothly, if jerking is distinct when the eye is at maximum deviation, and if the angle of onset of jerking is within 45 degrees of center. The NHTSA has concluded that if, between the two eyes, four or more "clues" appear, the suspect likely has a BAC of 0.10 or greater.

It is important to note that even the NHTSA acknowledges that the HGN testing allows for the proper classification of only 77 percent of suspects. That is, the HGN test will result in many false positives and cannot be considered a reliable indicator of intoxication. Indeed, the HGN is not admissible in Pennsylvania courts although police are permitted to use the test to establish probable cause to arrest. People taking medication such as seizure and psychiatric medication may also "fail" the HGN test even though they are not intoxicated.

2. Walk-and-Turn Test

In the walk-and-turn test, the subject is directed to take nine steps, heel-to-toe, along a straight line. After taking the steps, the suspect must turn on one foot and return in the same manner in the opposite direction. The examiner looks for seven possible indicators, or "clues", of impairment. If two or more clues are identified, a person is considered to be likely intoxicated.

It is important to note that even the NHTSA concedes that only 68 percent of individuals who exhibit two or more indicators in the performance of the test will have a BAC of 0.10 or greater. It is also important to note whether a person has some reason unrelated to intoxication - such as a physical disability, high-heeled shoes, use of prescribed medication, obesity, advanced age - that makes it more difficult to complete the test. It is very important to point out these issues to a judge or jury when a case goes to trial.

3. One-Leg Stand Test

In the one-leg stand test, a person is instructed to stand with one foot approximately six inches off the ground and count aloud by thousands (one thousand-one, one thousand-two, etc.) until told to put the foot down. The NHTSA protocols call for the officer to observe the subject 30 seconds. The officer looks for four indicators of impairment, including swaying while balancing, using arms to balance, hopping to maintain balance, and putting the foot down.

Prosecutors sometimes argue that a person's "failure" of field sobriety tests such as the one-leg stand test conclusively prove a person's intoxication. However the NHTSA itself admits that only 65 percent of individuals who exhibit two or more such indicators in the performance of the test will have a BAC of 0.10 of greater. And, like the walk-and-turn test, there are many factors other then intoxication that can make it difficult for a person to stand on one foot for 30 seconds.

It is important to carefully examine field sobriety test evidence. In many - if not most - instances, police officers do not administer the test in full compliance with NHTSA guidelines. For example, an officer's opinion should be considered suspect if he uses improper scoring criteria, was improperly trained, incorrectly instructed the suspect on how to perform the test or did not use the standardized methodology in performing the tests. Cross-examining police officers with their own training manuals frequently exposes their lack of knowledge and skill in conducting these tests. At trial, all of these factors must be fully explored so that a judge and/or jury understand the fallibility of field sobriety testing.

Blood Alcohol Testing

Pennsylvania state law provides that the police may not perform a chemical test of a driver's blood alcohol content (i.e., a breath test or a blood test) unless there is "reasonable grounds" to believe that the driver was operating a vehicle under the influence of drugs or alcohol. The police use field sobriety tests to help develop these "reasonable grounds" to submit motorists to chemical testing.

By law, people who drive a vehicle in Pennsylvania are deemed to have given their consent to providing a breath, blood or urine sample when requested to do so by the police if (and only if) the police have reasonable grounds and have arrested the person for DUI. Motorists who refuse chemical testing (assuming reasonable grounds to arrest exist) will have their license suspended for at least one year by PennDOT, and the fact that they "refused" the test may be used them at trial.

Whether a person is seeking admission into the Accelerated Rehabilitative Disposition (ARD) program or headed toward trial, it is important to carefully examine whether the police appropriately developed "reasonable grounds" to believe a driver may have committed a DUI. Where "reasonable grounds" are found not to exist, all subsequent chemical testing may be suppressed.

Alcohol is absorbed into the body through the stomach and small intestine over a considerable period of time. Alcohol has no physiological effect on the body or brain until it is absorbed into the blood stream. This absorption can take anywhere from 30 minutes, in the case of a dilute beverage and an empty stomach, to 2 to 6 hours with some beverages and a full stomach. Food in the stomach markedly delays the absorption of alcohol and reduces the peak level of blood-alcohol content as compared to a person with an empty stomach. Also, the ingredients in beer act like a food and delay the absorption of the alcohol found in beer. Alcohol is eliminated from the body at anywhere between 0.010 to 0.019 grams/deciliter/hour or 0.010 to 0.019 % per hour. The average person eliminates alcohol at approximately 0.015 % per hour.

The two most common chemical blood tests are blood testing and breath testing.

1. Blood Testing

Pennsylvania law requires hospitals and the physicians, nurses and technicians employed by hospitals to withdraw blood samples on DUI suspects unless there are emergency situations at the hospital at the time the request is made. Pennsylvania law also requires that blood (and urine) tests be performed at licensed and approved clinical laboratories using approved testing methods and equipment.

It is important to carefully examine blood test results to determine if the variance or margin of error may include the possibility that the true blood-alcohol content was in a lower tier or below 0.08 percent altogether. If a person's blood-alcohol content is tested to be, say, 0.10 percent, no toxicologist (or prosecutor) can say with any certainty that the person's actual blood alcohol concentration was above or below this level. Virtually every toxicologist will concede that there is a variance of 3 to 10 percent within which the actual blood alcohol content would likely fall.

Importantly, the Department of Health requires laboratories conducting blood-alcohol testing to test within 9 percent of a "known sample" in order to maintain their accreditation. Accordingly, many toxicologists contend that the margin of error of blood testing at such accredited labs should be presumed to be no less that 9 percent.

Even if someone elects to seek admission into the Accelerated Rehabilitative Disposition (ARD) program or plead guilty to DUI it is important to evaluate whether the documented blood-alcohol content can be reduced using a margin-of-error analysis. Anyone charged with DUI should carefully review all of these issues with an experienced criminal defense attorney.

2. Breath Testing

Police frequently test blood-alcohol content by subjecting the motorist to a "breathalyzer" machine. These machines are different from -- and much more sophisticated than -- the "portable breath test" units police use to test blood-alcohol content at the scene of the stop. To be admissible at trial, breath tests must be conducted in conformity with regulations set forth by PennDOT. These regulations require the machine to be regularly calibrated, the person operating the test to be certified, a 20-minute observation period prior to the testing, and two breath samples taken within a prescribed period of time. The two breath test results must be within 0.02 percent of each other. A failure of the police to comply with any of these regulations can result in the results being suppressed (ruled inadmissible) at trial.

As with blood testing, breath test results have a margin of error that should be considered in determining a person's actual blood-alcohol content. Persons charged with DUI must discuss these important issues with their attorney.

Contact a Pennsylvania DUI / ARD Attorney at  610-270-8800      

If you have been charged with Driving Under the Influence (DUI) in Montgomery County, PA, and want to consider admission into the Accelerated Rehabilitative Disposition (ARD) program or taking the case to trial, contact the experienced DUI / ARD attorney at the Law Office of Henry S. Hilles, III.