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The popularity of television shows such as "CSI" has increased the public's awareness of DNA as a crime-solving tool. Currently, most police departments in the United States—as a matter of policy and practice—collect DNA evidence only in violent crimes, such as homicide and sexual assault. This, in part, is based on the belief that it is too expensive to collect biological evidence (and perform DNA analysis) in high-volume crimes, such as property crime.
The facts that form the foundation of this belief, however, are changing. The cost of performing DNA analysis is decreasing. The amount of data in state and national DNA databases is increasing, and many DNA databases are now including the DNA profiles of all convicted (violent and nonviolent) felons. Based on information in these databases—and other research on criminal careers—researchers have found that many of those who commit property offenses do not "specialize," that is, they do not limit their activities to crimes against property and may commit other offenses, including violent crimes and drug deals.
For example, a Florida study revealed that 52 percent of that state's DNA database "hits" against murder and sexual assault cases matched individuals who were originally placed in the database for burglary convictions. A hit occurs when a database search of a DNA profile from biological evidence matches a profile in the database, thus identifying a suspect.
Learn more from the NIJ Journal article "DNA Analysis for 'Minor' Crimes: A Major Benefit for Law Enforcement."
Criminal justice experts have long known that those who commit property crime have high recidivism rates; the types of crimes they perpetrate—including the level of violence used—can escalate; and property crime cases frequently go unsolved. The Bureau of Justice Statistics estimates the average (mean) property loss from a household burglary in 2005 was approximately $1,500. Burglars often offend at high-rates and the total cost from their crimes may be many times this amount. Therefore, arresting burglars using DNA as part of the criminal investigation—burglars who otherwise would not be caught and brought to justice—has the potential to prevent future property and other crimes.
The DNA Field Experiment: Testing Cost Effectiveness of Collecting DNA in Property Crimes
In the past, the use of DNA to solve property crimes seemed like a poor investment — particularly if only the cost of an individual episode (and its related investigative costs) were considered. NIJ funded the Urban Institute to look at the effectiveness of performing DNA analysis of biological evidence collected from property crime scenes in five jurisdictions: Los Angeles, Topeka, Denver, Phoenix and Orange County (Calif.).
Inspired by the United Kingdom's successful experience in using DNA to solve property crimes, the NIJ field experiment looked beyond the individual and immediate property offense to the possible arrest of individuals who commit offenses at a high-rate. NIJ funding supported the purchase of supplies and equipment, as well as expenses of additional law enforcement personnel, prosecutors, crime laboratory personnel and outside DNA analysis services.
The results of the NIJ study challenge the belief that collecting and analyzing DNA evidence in property crimes is cost prohibitive. The study demonstrated that collecting DNA in property crimes, such as burglaries, is cost effective and dramatically increases the numbers of burglary suspects identified. The Urban Institute evaluation suggests that DNA collected from a property crime scene not only has the potential to prevent future property and violent crimes, but more individuals who commit burglary and serious violent offenses can be brought to justice, leading to safer communities.
The DNA Field Experiment was a collaboration between NIJ and local law enforcement agencies—police, crime labs and prosecutors—in five communities: Los Angeles, Topeka, Denver, Phoenix and Orange County (Calif.).
Major Findings from the DNA Field Experiment
Due to differences in policies, procedures and experiment implementation among the five jurisdictions, outcomes varied, sometimes substantially. Findings of the study, averaged across the five jurisdictions, were that when DNA evidence was collected at property crime scenes:
- Suspect identifications and arrests doubled. Twice as many property crime suspects were identified and arrested when DNA evidence was collected (in addition to fingerprint evidence) compared to a traditional property crime investigation.
- Cases accepted for prosecutions doubled. More than twice as many cases were accepted for prosecution when DNA evidence was processed than when it was not.
- The suspects arrested through DNA identifications were more dangerous. DNA arrestees had double the number of prior arrests and double the prior convictions as those arrested through traditional investigations.
- DNA was twice as effective in identifying suspects as fingerprints. In cases where both fingerprint and biological evidence were collected, more suspects were identified via the FBI's Combined DNA Index System (CODIS) than were identified via the FBI's Automated Fingerprint Identification (AFIS) system.
- DNA samples collected by patrol officers were no less likely to yield good evidence than those collected by forensic technicians.
- Among the cases in which biological evidence was collected, fingerprint evidence was collected in one-third of the cases.
- Comparing all cases:
- DNA was five times as likely to ID a suspect
- DNA was nine times as likely to yield an arrest
- Comparing cases with both types of evidence collected:
- DNA was twice as effective as fingerprints in identifying suspects
- DNA yielded three times as many arrests
- Comparing all cases:
- The average case cost to process DNA from the time the evidence was sent to the lab until an arrest was $1,397; there was little variation in costs, except that outsourcing (sending samples to a private laboratory) was more expensive.
- The additional cost of a new suspect identification was $4,514 (see full report for explanation and context [pdf, 164 pages]).
- The additional cost of a new arrest was $14,178 (see full report for explanation and context [pdf, 164 pages]).
- The additional cost of a new case that was accepted for prosecution was $6,913 (see full report for explanation and context [pdf, 164 pages]).
- The larger the state DNA database (percentage of state population), the more likely that an identification was made; this trend was revealed when comparing across sites and over the course of the study as California rapidly expanded its database.
How Was the DNA Field Experiment Performed?
Each jurisdiction in the study collected potential sources of biological evidence—along with conventional evidence such as fingerprints—from up to 500 property crime scenes between November 2005 and July 2007. The majority of the crime scenes were residential burglaries; the rest were commercial burglaries and automobile thefts.
- Step 1: Half of the cases were randomly selected to be analyzed to see if a DNA profile could be determined; the remaining half were not tested (or testing was deferred for a few months), thus serving as the control group.
- Test group (approx. 250/site) = Traditional investigation + DNA testing
- Control group (approx. 250/site) = Traditional investigation only
- Step 2: The test group samples were analyzed by a laboratory to determine a DNA profile.
- Step 3: DNA profiles were run against CODIS.
- Step 4: Investigative teams followed up on CODIS hits with further investigation and possible filing of charges.
Jurisdictions in the field experiment had to modify investigative and reporting procedures to accommodate the needs of the experiment—and, although they encountered challenges, most were met successfully. Many lessons learned through the field experiment offer "best practices" on using DNA forensics in solving property crimes.
Evaluating the DNA Field Experiment
The Urban Institute evaluated many aspects of the five-city DNA and property crime experiment, including the additional costs of using DNA analysis in a property crime investigation. The final report discusses:
- Cost to process DNA per case
- Cost paid by agency (police and the local/state laboratory)
- Cost per arrest/ID/profile
- Difference in outcomes (for example, the number of suspects identified and arrested with fingerprints vs. DNA)
- Types of cases with the greatest returns by:
- Evidence collector
- Type of crime (commercial, residential, motor vehicle)
- Type of evidence (cells, saliva, blood)
With respect to sample characteristics—and what they offer regarding best practices—blood samples were a highly significant predictor of outcome. When compared to cells collected from items that were touched or handled, blood samples were:
- 6 to 8 times more likely to result in a DNA profile suitable for CODIS upload
- 3 to 5 times more likely of yielding a CODIS hit
Saliva samples were more than three times as likely to yield a DNA profile, a CODIS upload and a CODIS hit than cells collected from items that had been touched or handled by the suspect.
Some Policy Implications of Using DNA to Solve Property Crimes
Findings from the five-city field experiment will be valuable to other cities and communities interested in implementing a policy and practice to collect DNA evidence in property crimes. The NIJ-funded study provides a variety of best practices and may also provide support as jurisdictions work with local lawmakers to provide funding for this law enforcement tool.
Even before the study was over, two of the five sites quickly moved to secure local funding to continue the program when NIJ funding ended. Indianapolis—a non-site city that learned of the project's successes—began developing a similar program of its own based on the preliminary findings from the study.
What should state and local jurisdictions look at when considering whether to adopt a policy for using DNA to solve property crimes?
Perhaps one of the most important lessons learned from the NIJ field experiment was this: a high level of collaboration between city police, county prosecutors and county and state crime labs is required to be successful. In the field experiment, as collaboration increased—fostered through biweekly conference calls, site visits and semiannual workshops—data systems and investigative processes improved.
Indeed, producing the most cost-effective results in the use of DNA to solve property crimes requires collaboration across multiple agencies: the police department, the crime laboratory and the prosecutor's office.