by Nancy Ritter
Research on DNA testing sexual assault kits reveals a complex picture.
It has been a headline-making story for the past few years: thousands of sexual assault evidence kits — untested — in police storage. In a few jurisdictions, lawmakers have responded to the outcry from victims and victim advocates by mandating that kits in all alleged sexual assaults be DNA tested.
But what do we know, empirically, about the value of DNA testing large numbers of sexual assault kits (SAKs) that have long been held in police property rooms? And what do we know, empirically, about the crime-solving utility of testing kits in all alleged sexual assaults?
One thing we know is that the probative value of forensic evidence in any crime, including sexual assault, depends largely on the circumstances of the case — pivotal in one, less important in another. If the perpetrator is a stranger to the victim, a DNA profile can be crucial in identifying the suspect and adjudicating the case. However, at least half of sexual assault victims know the perpetrator's identity; if he admits sexual contact but claims it was consensual, DNA evidence may be of questionable value in adjudicating the case — although it could have value in uncovering serial so-called "acquaintance" rapes. And, finally, when sexual assault is perpetrated on a child, DNA evidence is vital in determining that a crime occurred.
NIJ provided grant support to examine the role of DNA testing of untested SAKS in property rooms of the Los Angeles Police Department (LAPD) and the Los Angeles Sheriff's Department (LASD). The grant was modest — $100,000 — and, therefore, the study had a narrow focus, including time limitations.
The two primary goals in the L.A. study were to look at a random sample of the nearly 11,000 kits to:
- Assess the efficacy of DNA testing
- Determine the criminal justice outcomes (arrest, charge, conviction) within the first six months after the kits were DNA tested
The findings with respect to the study's second goal were surprising to many. In a randomly selected sample of 371 SAKs, there were no new arrests, new charges were filed in one case, and there were two convictions in the first six months after these kits were tested. In fact, it is probable that the DNA testing was not responsible for the single filing and the two convictions.
There are a number of important facts to keep in mind when trying to understand these results. First, the study looked at case adjudication in only the first six months after testing, as this was the period defined in the NIJ grant. The researchers did not examine whether there have been additional arrests, charges filed or convictions since that time. Second, the sample size was small, and the findings are from one site; therefore, great caution should be used in trying to extend the findings to other locales. Indeed, the reasons for large numbers of untested SAKs in police property rooms — and the testing and case status of the kits themselves — may be very different in other jurisdictions.
One possible explanation for the findings is that a large number of the more than 10,000 SAKs in police storage had not been sent to the laboratory precisely because detectives and prosecutors had previously determined that testing would not increase the likelihood of adjudication. It was, however, beyond the scope of the NIJ study to analyze why the kits in L.A. city and county had not been tested, except anecdotally through focus groups with detectives, prosecutors and laboratory analysts.
That said, the L.A. study findings provide more empirical knowledge in an area in which there has been relatively little solid research to inform an important, controversial challenge facing our nation today: untested evidence in sexual assault cases and the role of DNA testing in solving these cases.
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