How Far Should The DNA Dragnet Go?

New York Times

Updated July 14, 2010, 03:46 PM

Mitchell R. Morrissey is the district attorney of Denver. An expert in DNA technology and its application in criminal prosecutions, he introduced the first DNA evidence used in a criminal trial in Denver and maintains an online DNA resource.

The recent arrest of Lonnie Franklin for the so-called Grim Sleeper murders is a dramatic example of the value of using familial DNA searches. This arrest highlights the importance of employing every resource and investigative lead available, and reminds us that more than 95 percent of the victims of crime involving DNA are women and children.

When conducting a familial DNA search, investigators use specially designed software to search the DNA database for near matches to generate leads to help solve crimes, often rapes and murders. A near match indicates that the criminal who left the DNA at the crime scene could be the father, brother or sister of the offender whose DNA is in the database. This extra step was estimated by one study to provide a 40 percent increase in the number of investigative leads generated from a DNA database search. This could mean the difference between a serial rapist or murderer being caught or getting away with it, as the "Grim Sleeper" did for 22 years.

Increased public safety is the primary benefit of using familial searching software. DNA helps identify predators; familial DNA searching provides a science-based investigative lead in those cases in which a predator has avoided having his DNA added to the database. This procedure represents a solid first step, grounded in biology, statistics and genetics, which, in conjunction with traditional investigative work, can result in solving crimes and stopping a predator before he strikes again. Of equal importance to law enforcement and the community is the crucial ability of DNA to exonerate the innocent.

Familial searches, and the traditional investigation those searches yield, must be conducted in a legal and constitutional manner. The goal is always to provide investigators with a scientifically based lead while addressing privacy concerns. The familial search polices of the United Kingdom and in Colorado and California address the issues of privacy through a carefully crafted set of practices.

I believe we have a responsibility to use available technology in a constitutional and legal way to protect our communities. Familial searches extend the benefits of DNA technology to ensure that we are doing our best to prevent and solve crimes, and exonerate the innocent. By evaluating DNA evidence and providing leads for investigators, familial DNA searches save time, money and future victims.