Police Evidence

Evidence in a drunk driving case, including driving under the influence of drugs (DUID) and driving under the influence of marijuana (“driving stoned”), generally falls into five categories. The first of these consists of driving symptoms. Unless an accident is involved, this is usually what first attracts the police officer’s attention and, typically, may involve weaving, lane straddling or erratic driving. There are, in fact, 20 different driving patterns recognized by the National Highway Traffic Safety Administration which could be possible indicators of intoxication. Interestingly, speeding is not one of these; high speed actually requires better coordination, quicker judgment and faster reflexes.

The third type of evidence consists of field evidence, primarily consisting of field sobriety tests. These may include walk-and-turn, touch-the-nose, one-leg-stand, modified position of attention (also called the Rhomberg test), alphabet recitation, horizontal gaze nystagmus (following an object like a pen or finger from side-to-side with your eyes), fingers-to-thumb and hand pat. Federal studies have shown that only three of these (walk-and-turn, one-leg-stand and nystagmus) are effective in detecting intoxication; the others are unreliable and have been disapproved. As a result, a battery of three standardized field sobriety tests have been recommended and is increasingly being adopted by police agencies across the country. In California, however, police officers continue to administer whichever tests they choose. Contrary to popular belief, the tests are not compulsory; you may refuse to take them with no legal consequences.

Many police agencies are using a roadside breath-testing device (Breathalyzer) as an additional field sobriety test. Called PAS (Preliminary Alcohol Screening) units, or more recently EPAS (Evidential Portable Alcohol System), these hand held devices are supposed to give a very rough indication of the suspect’s blood-alcohol concentration. These PAS units are very primitive and unreliable and are supposed to be used only to aid the officer in making a decision after he has given the other field sobriety tests. Unfortunately, however, many judges are permitting the results into evidence at trial. Again, submission to a PAS test is not legally required (unless you are under 21 years of age).

The fourth category of evidence consists of incriminating statements, whether made spontaneously or in response to questioning. You are not, of course, required to answer any questions at any time. Since the Miranda warning need not be given until after the arrest, the officer is free to ask incriminating questions during his initial investigation. A refusal to submit to chemical testing may be interpreted as an incriminating statement.

The final type of DUI evidence is the blood-alcohol test. In a California drunk driving case, this involves a choice of breath or blood; urine was discontinued in 2000, except where neither breath nor blood are available. There are a number of different brands of breath machines used in California, but all are susceptible to numerous problems and none of them are reliably accurate. For one thing, the computer in the machine (Breathalyzer) assumes the person is average when, in fact, physiology and metabolism varies greatly. For another, if a person burps or belches, the breathalyzer will give a false high reading for about 15 minutes thereafter. In fact, the breathalyzer does not even measure alcohol, but rather the methyl group in the alcohol compound — and there are thousands of compounds that contain this group, over 100 of which have been documented on the human breath. Blood analysis is considerably more accurate, although possible problems exist there as well, such as fermentation of the sample, coagulation and lack of sterilization. Urinalysis is the least reliable test for blood-alcohol concentration.

For further materials and links concerning police evidence, including blood-alcohol testing, please visit our DUI law firm’s informational site, The Drunk Driving Law Center.