There are 2 types of evidence that the State relies upon in its attempt to prove a DUI case. The State's evidence can be roughly categorized into: (1) observations of professionally trained police officers and/or lay witnesses who were at the scene and observed driving or manifestations, and (2)
chemical testing of the defendant's blood, breath, or urine.
Both types of evidence in a DUI case are relevant to both the DUI per se and the "traditional" DUI less safe or impairment laws.
Most prosecutors place far too much weight on chemical testing and far too little weight on "field evidence."
Most prosecutors rely too heavily on chemical evidence; however, neglecting field evidence is a mistake. DUI field sobriety evidence corroborates the blood-alcohol reading, and when handled correctly and strategically, it can also serve to contradict that chemical test result.
Field evidence may be broken down roughly into five categories:
- Observations of the defendant's erratic or otherwise unusual driving (a suspect's driving recorded on video, in particular, is a critical piece of evidence in most DUI cases);
- Observation of the suspect's physical appearance, conduct, "normal manifestations";
- The defendant's performance on a field sobriety test, including the horizontal gaze nystagmus;
- Incriminating statements, including refusal to submit to blood-alcohol testing; and
- Audiovisual evidence (tapes, film, and/or photographs).
The importance of the DUI officer in the DUI case
Lay witnesses are "normal", untrained people that make observations of the facts of a case. Generally lay witness testimony is usually given less weight by the jury. Professionally trained witnesses (police officers) are usually the witnesses that provide the cornerstone of the State's DUI case. Usually, it is officer testimony that truly counts in the State's DUI case. The State presents these witnesses as well-trained, experienced, and “impartial” officers of the law. There are, of course, multiple means of challenging these witnesses.
5 general means of attacking law enforcement
- Questioning qualifications and experience in the very limited area of drunk driving;
- Establishing his predisposition to believe the defendant guilty at initial stages of the field detention;
- Suggesting innocent explanations for incriminating observations;
- Emphasizing the observations that tend to establish the defendant's sobriety;
- Attacking the officer's observations, interrogations, and testing producers…including procedures the officer failed to follow.
Some general guidelines for approaching the challenge to police officer opinions
- Deal with each officer on an individual basis, understanding at all times the jurors attitudes toward his questioning.
- Police officer: a professional witness. Usually a fairly skilled adversary who should he viewed as such;
- Each officer is different.Officer's age and experience play a role in his alcohol-related arrest decisions. Younger officers, and those with relatively few years of seniority, tend to have a more positive attitude toward alcohol-related enforcement and make more arrests than do older officers.
- Personal use of alcohol is inversely related to his level of alcohol-related enforcement.
- Lack of knowledge concerning the relationship between alcohol and intoxication is widespread among police officers and imparts a negative influence on alcohol-related enforcement.
- Specialized training has a strong positive influence on alcohol-related arrests. Specialization in duty assignment can also enhance alcohol-related enforcement.Near the end of the duty shift, alcohol-related investigations decrease substantially.
- Weather conditions also affect alcohol-related arrests.
- The suspect's attitude can have a strong influence on the arrest/no arrest decision.
- The suspect's race is a key distinguishing characteristic in alcohol-related cases.
- The data do not suggest that this reflects a greater tendency to exercise discretion when dealing with non-white drivers. Officers seem more willing to initiate an investigation when the suspect is not of their own race.
- Patrolmen reported releasing significantly more young suspects than they arrested.
- Young officer's exhibit more sympathy for young suspects, i.e., seem less disposed to arrest a driver of their own age group.
- Older officers seem more willing to stop young suspects, i.e., are more likely to conduct an investigation when the driver is young.
- Suspect's sex also plays a role in the arrest/no arrest decision. Reluctant to arrest a woman for alcohol-related violations.