The DNA evidence backlog picture is complex and requires an understanding of the types of backlogs that exist and the ways crime laboratories work.
Defining the Backlogs of Forensic DNA Evidence
There is no industrywide definition of a backlog. Some laboratories consider a case backlogged if the DNA has not been analyzed after 90 days. Others consider any case backlogged if the DNA has not been analyzed and the final report has not been sent to the agency that submitted the DNA. NIJ defines a forensic biology/DNA backlogged case as one that has not been completed within 30 days of receipt in the laboratory.
Discussion of and research about backlogs must take into consideration the varying definitions of the term. In addition to delineating length of time, it also is important to identify the type of backlog being referenced. There are two types: (1) casework backlogs and (2) convicted offender and arrestee DNA backlogs.
|Casework||Convicted Offender and Arrestee DNA|
Forensic evidence is collected from crime scenes, victims and suspects in criminal cases and then submitted to a laboratory. Processing this evidence is time-consuming because it must first be screened to determine whether any biological material is present and, if so, what kind of biological material it is. Only then can DNA testing begin. In addition, some samples can be degraded or fragmented or may contain DNA from multiple suspects and victims.
DNA samples are taken from convicted offenders and arrestees pursuant to federal and state laws. It is significantly easier and faster to analyze these samples than casework samples because they are collected on identical media (usually a paper product). The standardized collection methods in each state allow the laboratory to use automated analysis of many samples at once. Robotic platforms, for example, can process scores of these samples and the appropriate controls at the same time, generally in a 96-sample format. In addition, unlike with forensic casework samples, the laboratory analyst does not need to "find" the DNA amidst the evidence.
The processes and procedures used in casework DNA testing are somewhat different from those for convicted offenders and arrestees. Thus, the two types of backlogs should be considered and discussed separately to avoid the common mistake of "comparing apples with oranges."
Untested Evidence in Law Enforcement Agencies
A related but quite different problem involves untested evidence collected from crime scenes and stored in law enforcement evidence rooms that has not been submitted to a crime laboratory for analysis. NIJ considers untested evidence awaiting submission to laboratories to be a matter separate and different from backlogs in crime laboratories. Federal funding programs to reduce backlogs in crime laboratories are not designed to address untested evidence stored in law enforcement agencies.