Scientific & Legal Defenses to a DUI Charge

The legal limit in Michigan is .08, but there are several scientific and legal defenses to a drunk driving charge. Government ad campaigns and slogans such as, "Over the Limit, Under Arrest," coupled with a misguided faith in the legal system result in many wrongful convictions. Unwittingly, innocent people accept plea agreements every day based upon faulty chemical tests. In other instances, guilty people plead guilty when legal defenses could have been successfully raised. The vast majority of DUI cases go unchallenged.

Machines, as well as police officers, make mistakes. A person accused of operating while intoxicated should never be overwhelmed by misgivings and doubt just because the government's machine claims that the driver was above the legal limit. Likewise, a guilty person should never assume that the police officer's case is rock solid. Police officers who make mistakes typically acknowledge those mistakes, and simple human error can result in a dismissal.

Field Sobriety Tests

Field sobriety tests are supposed to be able to determine whether a person is intoxicated. Police officers might request that a motorist recite a portion of the alphabet, count backwards, or engage in a variety of dexterity tasks, e.g. finger to nose, finger-count, pick a number, etc. The Standardized Field Sobriety Test battery (SFSTs) have studied and supposedly validated three specific tests described as the Horizontal Gaze Nystagmus test (HGN), the Walk and Turn test (WAT), and the One Leg Stand test (OLS). Without chemical test evidence, a prosecutor may submit evidence of a person's performance of these tasks to a jury in most jurisdictions as substantive evidence of impairment and intoxication.

Field sobriety tests blur the distinction between direct and circumstantial evidence. A motorist who cannot say his or her alphabet or walk heel-to-toe might be perceived as intoxicated, but it is reasonable to question this evidence. Judges describe the difference between direct and circumstantial evidence to jurors as follows: "Direct evidence is evidence about what we actually see or hear. For example, if you look outside and see rain falling, that is direct evidence that it is raining. Circumstantial evidence is evidence that normally or reasonably leads to other facts. So, for example, if you see a person come in from outside wearing a raincoat covered with small drops of water, that would be circumstantial evidence that it is raining." Although police officers and prosecutors will deny it, a person's inability to perform a heel-to-toe test is direct evidence that the person could not perform it, and nothing more. At best, the inability to perform the test provides only circumstantial evidence that the person might be intoxicated. Because field sobriety tests are not nearly as accurate or reliable as they purport to be, the evidence drawn from these tests may cross from permissible circumstantial evidence into the realm of impermissible speculative evidence.

Wrongful convictions of absolutely innocent people can result from reliance on the field sobriety tests. As an example, police and prosecutors claim that the HGN test is the most accurate test. A recent study produced by the federal government to support this claim released raw data that directly contravened the study's findings. The raw data conclusively proved that the most highly trained police officers working under laboratory conditions incorrectly identified 77% of alcohol-dosed subjects as being over .08 when they were under the legal limit. Nearly 40% of the false arrest decisions involved subjects under .05, even though these officers would have provided compelling testimony to jurors had this occurred roadside.

Continue to Scientific Defenses: Breath, Blood and Urine Testing