Banner for The Criminal Justice Systems: A Guide for Law Enforcement Officers and Expert Witnesses in Impaired Driving Cases


The criminal justice system is far more complex than most people understand— it entails more than a crime, an arrest, a trial, and either a conviction or an acquittal. You, the law enforcement officer or expert witness, through your profession, have been invited by a subpoena to testify. What does it all mean? How much time is it going to take? What will you be asked? Why do you have to be involved?

This publication will provide you some guidance as to what it means to be a witness, what you can likely expect, and the importance of your role. It also provides an overview of the complexities of the criminal justice system to help explain why you may be called to testify more than once, and asked the same questions on the same subject for the same case. It is intended as a guide to help answer some of your initial questions and concerns. Detailed answers may come from colleagues who have previously testified in court, as well as from the attorney who subpoenaed you to testify.