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


While common in occurrence, the evidence needed to prove guilt in impaired-driving cases is complex, often requiring expert testimony to assist the trier-of-fact in determining what happened. As in any profession, those who work in it sometimes take for granted the complex nature of our legal system and presume others understand it as we do, which oftentimes is not the case. To fill that void, this publication provides an overview of the criminal justice system for people who will likely encounter it through their roles as expert witnesses.

This guide is the result of a collaborative effort on the part of the following: Debra Whitcomb, Director of Grant Programs and Development, National District Attorneys Association; Marcia Cunningham, Director, National District Attorneys Association’s National Traffic Law Center; Joanne Michaels, Senior Attorney, National District Attorneys Association’s National Traffic Law Center; L. R. “Bob” Jacob, of the Institute of Police Technology and Management (IPTM), Jacksonville, Florida; and George Dentes, former four-term District Attorney for Tompkins County, New York  (1989-2005). Sadly, Mr. Dentes died unexpectedly on October 31, 2006, just steps away from his office at the New York Prosecutors Training Institute.