In order to prosecute a person for DUI, the police need to collect sufficient evidence to prove the driver’s guilt beyond reasonable doubt. Thus, various kinds of evidence are are obtained during investigations. Among these are as follows:
Driving symptoms. These usually catch the police officer’s attention which may involve swerving between lanes, running while a stop sign, lane straddling or erratic driving. As recognized by the National Highway Traffic Safety Administration, there are about 20 different driving patterns which could be possible indicators of intoxication. However, it is interesting to note that speeding is not one among these driving symptoms for speeding is said to require better coordination, quicker judgment and faster reflexes.
Personal behavior and appearance. During a DUI stop, the police will examine whether the driver is intoxicated which may be evidenced by having odor of alcohol, disheveled clothing, bloodshot eyes, unkept hair, slurred speech, flushed face, fumbling with a wallet to get the driver’s license, unsteady gait, leaning on the car for support, difficulty following directions, etc.
Field sobriety tests. These are among the most controversal aspects of a DUI stop. These may include testing the body’s positioning and balance (also called the Rhomberg test or the Romberg maneuver), alphabet recitation, horizontal gaze nystagmus (involves following an object with the eyes, usually a pen), fingers-to-thumb and hand pat. Although these field sobriety tests have been continually used, only three of these (walk-and-turn, one-leg-stand and horizontal gaze nystagmus) are adopted and considered effective by the NHTSA. In some states, only these three standardized tests are admissible in evidence. In California, however, police officers continue to administer whichever tests they choose. Undergoing these tests is not compulsory and does there is no law that punishes anyone who refuses to take them.
Breathalyzer. Known as PAS (Preliminary Alcohol Screening) units, or EPAS (Evidential Portable Alcohol System), these hand held breathing devices are supposed to give a very rough indication of the suspect’s blood-alcohol concentration. However, despite their relative inaccuracy, courts have permitted the admission of evidence at trial. But submission to a PAS test is not legally required (unless the person is under 21 years of age).
Miranda warning. This warns the person from making incriminating statements, whether made spontaneously or in response to questioning. “Every person has the right to remain silent”. The officer is free to ask incriminating questions during initial investigation before the Miranda warning is given. A refusal to submit to chemical testing may be interpreted as an incriminating statement.
Blood and breath test. These tests are given after performing the other tests and the police officer has reasonable belief that the driver has been drinking or abusing drugs. The machine called the breathalyzer is susceptible to numerous problems and often yields inaccurate results. It 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.