Driving Symptoms

The first type of evidence that will be presented to the jury by the prosecution will be the arresting officer's observations of the defendant's erratic or otherwise unusual driving symptoms—what attracted the officer's attention in the first place. In the rare case where the officer witness did not observe driving, such as where there has been an accident, then that portion of the corpus delicti will be supplied by lay witnesses or by circumstantial inference.

How important are the driving symptoms in a DUI case? Most DUI defense attorneys would probably consider the blood-alcohol evidence to be the most critical, followed perhaps by field sobriety tests. But the view of many experienced prosecutors is that the single most important area in obtaining a conviction is police testimony concerning the defendant's driving.

A manual prepared by one of the largest prosecuting agencies in California recognizes four major categories of evidence: driving symptoms; appearance and demeanor; FSTs; and blood-alcohol test or refusal. Of these, the manual states, driving is the most important—and field sobriety tests, "which are not generally viewed by jurors as highly persuasive," the least.

While the author does not necessarily agree with this view, it may be helpful to understand what the view of one's opponent may be.

Typically damning testimony would involve the officer initially observing the defendant's car traveling at a high rate of speed. For example: as the officer began pursuit, the officer noticed that the car weaved across lane lines on five occasions; at one point, the defendant failed to stop for pedestrians who were crossing in an intersection. When the officer finally decided to turn on his flashing red lights, the defendant failed to pull over for a quarter of a mile; when he did, he parked at an odd angle to the curb, the rear of his car presenting a hazard to passing traffic.

How does the DUI lawyer deal with testimony of damaging driving symptoms? Each case is different, of course, but it is rarely productive to engage in a frontal attack on the officer—to premise a defense on the sole theory that the officer is a liar and is trying to hang your client for some unknown reason. The usually more effective approach is to take each observation, one at a time, and suggest reasonable explanations for the observed conduct—and thus, a reasonable explanation for why the officer believed (mistakenly) that the client was intoxicated.


Consider first the officer's testimony that the defendant was speeding. One tactic is to ask the officer how many speeding tickets he has issued in his career—and how many of those involved drunk driving. The answer to this last question should be "none," of course, since an officer arresting someone for drunk driving rarely bothers to issue a speeding citation as well. But this simple line of questions presents issues which can later be developed in arguments to the jury.

  1. If speeding is symptomatic of drunk driving, why has the officer never found speeding to be involved in any of his DUI arrests?
  2. If speeding is not a symptom, then why was the officer attempting to present it as evidence of intoxication?
  3. If the defendant was speeding, why wasn't he cited for it?

DUI attorneys must, obviously, keep a tight rein on the officer during cross-examination and not permit the officer to offer explanations. If the subject is not explained in redirect, then the issue should be discussed during argument.

Evidence of speeding can be turned to the client's advantage. This involved leading the DUI officer into admitting that controlling a car requires more coordination and greater judgment as speed increases. Quite simply, driving a vehicle at the speed observed by the officer without having an accident requires considerably greater reflexes, coordination, and judgment than at the legal speed. Thus, the very fact of speeding without mishap is evidence of sobriety. In other words, rather than trying to prove the client was not speeding, counsel should simply accept the fact and turn it to his advantage. The natural tendency of the trial lawyer to contest everything should be overcome; the client is not on trial for speeding.


The next driving symptom almost universally encountered in DUI cases is "weaving." In fact, along with "alcoholic breath," "thick and slurred speech," and "bloodshot eyes," it seems nearly a prerequisite to any arrest for drunk driving. And, without question, there are officers who will add these symptoms to their reports to create the classic DUI scenario. In most cases, however, the officer is honest—but guilty of suggestive perception: once he has decided that the suspect is possibly under the influence, he expects to see the usual symptoms —and normal inattentive driving becomes "weaving."

DUI lawyers must develop through cross-examination of the officer that weaving is not nearly as unusual or symptomatic of intoxication as it sounds. The officer should be led to admit that no driver steers a car in a geometrically straight line dead center in the lane; only railroad cars travel perfectly straight. During argument, the jurors should be reminded that even the most sober of them will find that as one drives one is constantly, perhaps subconsciously, correcting course with a back-and-forth motion of the steering wheel. So it is a matter of degree—and of the mechanical condition of the car.

The mechanical condition of the client's car at the time of arrest should not be overlooked in preparing for trial. A thorough inspection by a licensed mechanic may well produce a valuable defense witness, since mechanical problems can cause weaving and other erratic driving symptoms. Testimony that the car had bent tie rods, a sticking accelerator, defective suspension, worn brakes, faulty steering, improperly inflated tires, or poor wheel alignment, can be effective. Even without such a witness, the possibility of such mechanical problems can be brought out in cross-examination of the officer.

An effective technique in dealing with bad driving symptoms is to establish how long the officer followed the client and then to ask him about the effects of "black-and-white fever." Some officers will know it by another name, but the phenomenon is known. That phenomenon is simply the normal reaction of most drivers to being followed by a marked police car (painted, in many jurisdictions, black and white). As soon as the motorist becomes aware that a police car is following, the motorist becomes understandably apprehensive—and focuses his or her attention increasingly on the rear view mirror. As the officer continues to follow, the driver becomes tense, worried, the driver's concentration on driving broken. The driver keeps his or her eyes more on the mirror and less on the road ahead. As a result, the driver must constantly correct the course of the car back to the center of the lane. Thus, the phenomenon observed by the officer: "weaving"—and, possibly, erratic movements such as sudden increases or decreases in speed (tension can cause the foot to depress the accelerator).

The honest and experienced officer will readily admit—often with some humor—that this reaction is a common occurrence. In the event that the officer does not, however, there will certainly be 12 people sitting nearby who will recognize this situation from their own experience.

Suppose the defendant failed to stop at an intersection, narrowly missing a pedestrian. This observation can also be attributed to "black-and-white fever": the driver was watching the police car in the rearview mirror and did not notice the pedestrian in the crosswalk. And, as with speeding, counsel can establish through the officer that failure to stop is a common violation and not necessarily symptomatic of inebriation. Again, has the officer ever cited anyone for failure to stop who was under the influence?

At this point, the DUI defense attorneys might consider asking the officer why he or she had not pulled the defendant over earlier after observing suspicious driving symptoms. Why was the defendant not stopped after he or she was seen speeding? Why not after the apparently serious weaving? If the defendant ran an occupied crosswalk, why was the stop not made then? Of course, the form of questioning must continue to be leading and the witness tightly controlled. But the critical point here is a simple one: the observations of the client's driving couldn't have been too bad or he or she would have been pulled over immediately or at least much earlier. The officer may counter by saying the officer wished to be fair to the suspect by observing him or her for an extended period of time, or perhaps by testifying that the officer was "gathering evidence" by the extended observations. This, of course, can be in turn countered by asking him or her about the primary duty of the officer: to protect the public. Permitting a drunk driver to continue to endanger lives in the name of "fairness" or "evidence gathering" is clearly contrary to the officer's duty—and the officer will be hardpressed to deny it.

Again, the point here is not that the traffic infractions never occurred, but rather that:

  1. The infractions were not such as to indicate to the officer that the defendant was a danger to others on the road, that is, intoxicated.
  2. The driving symptoms were not sufficient—even when viewed in their totality to justify detaining (if subsequent detention was only after also smelling the breath, hearing the speech, or other symptoms) or arresting the defendant.

Defendant's Failure To Pull Over

The officer's next observation may involve the client's failure to pull over after the siren or flashing red lights were activated. Once again, the tactic of the DUI lawyer is not to disprove that this happened, but rather to offer a reasonable explanation. For example, it is not unusual, and thus not evidence of inebriation, to be unaware of flashing lights to the rear, particularly during daylight hours. If the client saw the lights, he or she may have assumed that they were intended for someone else — not an unreasonable assumption for someone who believes he or she has done nothing wrong. Or the client may have reasonably believed that it was an emergency and he or she was to get out of the way (which the officer will see as more weaving or an unsafe lane change). If the siren was then used, counsel should develop the increasingly common problem familiar to officers, fire fighters, and ambulance drivers, of motorists being oblivious to sirens because of air conditioning and car stereo systems. With the windows rolled up, the air conditioner on and the stereo blaring through large door-mounted speakers, it is hardly a surprise that many drivers do not hear sirens.

Manner of Pulling Over

The DUI officer may testify that when the client did finally pull over, the client parked at a dangerous angle to the curb—indicating the poor judgment and coordination of the drunk driver. It can also indicate, however, a very nervous and frightened driver. The officer should be asked if he or she has observed this type of parking in cases involving routine traffic citations, and if it is common for drivers who are pulled over to be flustered and apprehensive. With blood pressure rising and adrenaline pumping, totally sober drivers have been known to cause traffic accidents under such circumstances. If the officer chooses to deny this, jurors who have been pulled over may begin to doubt his entire testimony; few jurors would react coolly and dispassionately to being pulled out of traffic with flashing lights and sirens.

The DUI attorney should not limit the inquiry to what the officer has testified he or she observed: counsel should also bring out what the officer did not observe. Some experience with DUI cases is helpful here. The officer can be asked if alternately speeding up and then slowing down can be a symptom of drunk driving — or, in the alternative, has the officer seen such driving in past DUI cases. If so, did the officer observe this type of driving with the defendant? Was the defendant going off on the shoulder of the road? Was the defendant obstructing traffic by traveling too slowly? Did the defendant run any red lights? Did the defendant cause any other cars to swerve to avoid him or her? What the officer did not observe can be as relevant to the issue of inebriation as what the officer did observe.

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