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Unanalyzed Evidence in Law Enforcement Custody

United States Department of Justice

More than 2,000 state and local law enforcement agencies responded to a survey [1] to:

1. Estimate the number of unsolved homicide, rape and property cases [2] nationwide that contain forensic evidence that has not been submitted to a crime laboratory for analysis.

2. Determine the existence of policies and procedures regarding the processing, submission to a lab and retention of forensic evidence.

The survey showed that agencies had not submitted forensic evidence (including DNA, fingerprints, firearms and toolmarks) to a crime lab in:

* Fourteen percent of open, unsolved homicides.
* Eighteen percent of open, unsolved rapes.
* Twenty-three percent of open, unsolved property crimes.

There are reasons why a law enforcement agency may not submit forensic evidence to a lab. The evidence may be considered not probative, charges may have been dropped or a guilty plea entered. However, the researchers who conducted the NIJ-funded survey also concluded that some law enforcement agencies may not fully understand the value of evidence in developing new investigative leads.

Learn more about why evidence may not have been submitted.

The survey also revealed that:

* Only four out of 10 law enforcement agencies have a computerized system for tracking forensic evidence either in their inventory or after it is sent to the crime lab. Learn more about the use of computerized systems.

* Policies and practices for evidence retention varied widely from jurisdiction to jurisdiction. Learn more about policies and practice.

* There are steps that law enforcement agencies, forensic laboratories and prosecutors can take to improve the use of forensic evidence. Read a summary of the study recommendations.

The survey did not determine:

* How many of the open cases would be solved or yield investigative leads if evidence in them were to be sent to the lab.

* The number of cases in which evidence was analyzed in the past, but which now, with more advanced technology, might be solved or yield investigative leads. Read more about the potential value of the evidence.

Why Evidence May Not Be Sent to a Lab
There are many reasons why evidence collected from a crime may not be submitted to a laboratory for analysis. Subsequent investigation may have shown that the evidence would not be probative, charges against an alleged perpetrator may have been dropped, the suspect may have pled guilty, or, in a rape case, the issue may be "consent" and, therefore, analysis of the evidence may have been considered not probative.

However, the study showed that some law enforcement agencies do not fully understand the potential value of forensic evidence in developing new leads in a criminal investigation; for example:

* Forty-four percent said one of the reasons they did not send evidence to the lab was because a suspect had not been identified,

* Fifteen percent said they did not submit evidence because analysis had not been requested by a prosecutor.

We know that DNA evidence can identify a suspect in a "no suspect" case or link a perpetrator to a specific crime through CODIS, the national DNA database, and latent prints can identify unknown perpetrators through automated systems like the national Integrated Automated Fingerprint Identification System (IAFIS). The knowledge gap revealed in some of these findings — particularly, as the survey reveals, among the nation's small (less than 25 officers) agencies — could be due to a lack of training. Specialized training in these cases may have been beneficial and led to a different outcome. In another finding from the study, 11 percent of the agencies reported that one of the reasons they do not submit evidence for analysis is because of the lab's inability to produce timely results, and 6 percent said the lab was not accepting new evidence due to backlog issues. (See About the Backlog on

See Reasons Why Law Enforcement Agencies did not Submit Forensic Evidence for Unsolved Cases (pdf, 81 pages) in the full report.

Many Agencies Lack Computerized Systems
Computerized information systems enhance the ability of police agencies to manage, track and monitor forensic evidence in criminal cases. The survey revealed that more than half of law enforcement agencies (56 percent) did not have a computerized information system that was capable of tracking forensic evidence inventory. Large agencies (100 or more sworn officers) were much more likely to have a computerized system, with nearly three out of four reporting that their information system allowed tracking of forensic evidence.

For the agencies that do have a computerized information system, the survey did not reveal the exact capabilities, such as whether they were able to specify what evidence has been tested (or not tested) in a case, how long evidence in a case has been in storage, and the status of cases. The survey also did not determine, for the 44 percent of agencies that do have a computerized system, whether these systems are integrated with more centralized police records management systems.

See Law Enforcement Information Systems and Forensic Evidence (pdf, 81 pages) in the full report.

Many Agencies Lack Policy, Practice
Policies and practices for retaining evidence varied widely from jurisdiction to jurisdiction. In addition to the need to retain evidence in unsolved crimes, there are an increasing number of states that have passed laws requiring the indefinite storage of forensic evidence used in criminal convictions. About a third of the agencies (38 percent) said they had an evidence-retention policy regarding the preservation of biological evidence in cases where the defendant was found guilty, and 16 percent said they were unsure if they had such a policy.

Among agencies that do have a policy regarding the retention of evidence post-conviction, 51 percent reported that the policy was governed by state statute, 43 percent said evidence was retained due to agency policy, and 5 percent said the policy was in place as a result of a legal decision.

See Law Enforcement Policies for Retaining Biological Evidence (pdf, 81 pages) in the full report.

Recommendations for the Future

The researchers made a number of recommendations:

* Increased training for law enforcement on the benefits and use of forensic evidence, including guidelines for prioritizing cases for analysis.

* Creation (or improvement) of information management systems to track and monitor forensic evidence.

* Development of better protocols to ensure timely submission of probative forensic evidence to the lab and standardized policies for evidence retention.

* More storage capacity for analyzed and unanalyzed forensic evidence.

* Better coordination within a law enforcement agency and among the police, forensic lab and the prosecutor's office. Coordination could involve dedicated staff for case management, regular team meetings for case review and case tracking systems to allow information-sharing across these agencies.

* More research to better understand (1) what proportion of the open cases might be solved or yield investigative leads if evidence was submitted to a lab and (2) how such cases should be prioritized for testing.

See Study Implications (pdf, 81 pages) in the full report.

The Potential Value of Unanalyzed Evidence not Addressed
The survey does not reveal how many open cases with unanalyzed evidence would be solved or yield investigative leads if evidence were to be sent to the lab. It also does not address the number cases in which evidence was analyzed in the past, but which now — with the benefit of larger offender databases and new forensic technologies — might be solved or yield investigative leads; for example, a latent print run through IAFIS several years ago with no successful match could yield a hit now. More research would help us better understand these issues.

See Study Limitations (pdf, 81 pages) in the full report.

About the Survey Responses
The 72 percent response rate for the survey is considered very good; 2,250 of the 3,094 state and local law enforcement agencies that the survey was sent to responded. In some jurisdictions, however, the number of unsolved cases containing unanalyzed evidence was based on estimates; and some of the larger county and state agencies reported difficulty providing information about rape and property cases because they do not maintain these cases in a centralized system.

See Study Limitations (pdf, 81 pages) in the full report.


[1] Strom, Kevin J., Jeri Ropero-Miller, Shelton Jones, Nathan Sikes, Mark Pope and Nicole Horstmann, The 2007 Survey of Law Enforcement Forensic Evidence Processing (pdf, 81 pages), Final Report, Washington, DC: U.S. Department of Justice, National Institute of Justice, September 2009, 228415.

[2] Unsolved cases were defined as cases that had not been officially cleared by the law enforcement agency.

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