How does a police officer testifying in a drunk driving trial recall every detail of a DUI investigation months earlier?

When an officer stops a motorist and suspects that he may be under the influence of alcohol, he begins to mentally record various observations. Was the driving erratic, and in what way? What was his reaction to the red overhead lights? How did he pull over and park? Was there an odor of alcohol on the driver’s breath, and how strong? Could it have come from the passenger? Was the driver’s face flushed, eyes bloodshot, speech thick and slurred? How did he respond to questions and directions? What were his answers to questions such as "Where are you going? What time is it? Have you been drinking? What? When? Where? How much?" Did he have a current license and registration? Did he fumble with his wallet pulling out his license? Stagger when stepping from the car? What did the passenger say? How did she appear? And so on.

Then there are the DUI field sobriety tests. How did he perform in the walk-and-turn test? Did he understand the instructions? Did he start before I told him to? How many steps out? How did he turn? How many steps back? Which, if any, of the 18 steps were off the line? Where did they land? Which, if any, were not heel-to-toe? Was he using his arms for balance? Did he say anything during the test?

And the other three or four drunk driving field tests…

In the "horizontal gaze nystagmus" ("Follow my pen with your eyes without moving your head") test, was there "smooth pursuit" of the right eyeball? What did it look like? How many times was it given? Did "onset" of nystagmus occur before 45 degrees? At what degree? Was I able to see the white of the eye at the extreme range of the eye? Was there "distinct nystagmus" at this extreme? And what about all these observations in the left eye?

And maybe two or three other field sobriety tests.

And then the arrest and the breath test at the station: What was the procedure used to administer the test? What messages were displayed by the machine in preparation? Did the suspect say anything about a medical condition? How many breath samples were captured? Was there a blank test run before each sample test? What were the readings of the blanks? Of the suspect’s two samples? And so on….

In other words, there are a vast number of things to remember about what happened in the course of a properly conducted drunk driving investigation — and in dozens of other investigations. And the officer may have to testify some day in trial about all of these things. This has to be done from memory and under oath. How does he do it?

Well, typically the officer sits down an hour or two after the arrest and writes out a "DUI arrest report". This has to be from short-term memory (few officers attempt to write down notes in the field: it is usually dark, one hand is tied up with a flashlight and police policy requires that the "gun hand" be free at all times). This report may be only a couple of pages, or it may run to five or six pages. And this creates two basic problems….

First, how can the officer remember an hour or two later everything that happened? Imagine just one of the field sobriety tests, for example. In the walk-and-turn test, there are 18 steps — 9 out, 9 back. Most DUI reports have diagrams for the tests; in the walk-and-turn, there will usually be two arrowed lines, with the officer placing circles for the right foot and triangles for the left foot for each step on each of the two out-and-back lines: 18 circles and triangles. How is this officer able to recall an hour or two later each of 18 steps and exactly where each landed in relation to the line, at what angle and whether heel-to-toe? And this is just one test. And what about the driving pattern, the symptoms, the defendant’s statements, his conduct, and all of the other details?

Second, how can the officer recall three or four months later in trial everything that happened? He can’t just read from the report: He has to testify to what he knows — that is, to what he independently remembers happened. But here the law permits him an "out": He can "refresh his recollection" by reading the report after he is asked a question. Then he can testify with a newly "refreshed" memory — in reality, to what he wrote in the report. In most trials, the officer has also "refreshed his recollection" just before testifying, and/or does so repeatedly during his testimony.

Problem: The report only contains incriminating facts.

The officer was gathering evidence against the suspect: he only wrote down what he saw and heard that pointed to the defendant’s GUILT. He did not bother to record facts which pointed to the defendant’s innocence. He did not, for example, write down that the defendant had no trouble maintaining his balance or that his eyes were not bloodshot. In other words, in trial he is incapable of testifying to anything that indicated the defendant may not have been under the influence of alcohol. No matter how honest the officer is in his testimony, he simply cannot "refresh his memory" about things that happened but which are not in the report. And there will be little if anything in that report which will give "the other side" of the story.

Put another way, the most important witness in the trial is mentally incapable of recalling any evidence which may point to the defendant’s innocence.