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Role and Impact of Forensic Evidence in the Criminal Justice System, Executive Summary

NCJ Number
Tom McEwen
Date Published
December 2010
12 pages
This is the executive summary of the report on a study of the role and impact of forensic evidence in the criminal justice system conducted by the Institute for Law and Justice, Inc.
The study tracked cases and forensic evidence through local criminal justice processes (Denver, CO, and San Diego, CA) for homicides, sexual assaults, aggravated assaults robberies, and burglaries. Two smaller studies involved a survey of 75 police departments in order to obtain information on the organizational placement, staffing, and responsibilities of crime-scene units, as well as an analysis of an experiment in the Miami-Dade Police Department (FL) to determine whether clearance rates for non-suspect property crimes could be improved through faster processing of DNA evidence. One of the key findings from the processing of serious cases was that forensic evidence is collected in almost all homicides and the majority of sexual assaults, but the collection of such evidence declines significantly for aggravated assaults, robberies, and burglaries. Another key finding is that the majority of forensic analysis for closed cases occurred after arrest, which shows the importance of forensic analysis in supporting arrests and in preparing for prosecution. Study findings also show that the CODIS and AFIS databases continue to play important roles, especially in cases where investigators have exhausted all leads and no arrests have been made. Coordination between investigators and prosecutors is essential in the use of "hits" from these systems. The study found that most defendants charged with homicides and sexual assaults had forensic evidence involved in their cases, and the majority of these defendants received guilty dispositions. Guilty defendants in cases with probative evidence received longer sentences. The survey of police agencies showed no consistency on types of personnel, organizational placement, and number of personnel in crime-scene units.