DNA Testing

  • Share
  • Read Later
Owen Franken / Corbis

A person works with DNA samples

As most any episode of CSI will tell you, DNA testing is a staple of modern crime investigations. But only now is the U.S. Supreme Court wading into the murky legal terrain surrounding high-tech fingerprints in forensics. A sharply divided court ruled on June 18 that prisoners do not have a constitutional right to DNA testing that could prove their innocence, deciding against an Alaska man convicted of rape and assault who sought a more sophisticated test of genetic material found at the crime scene. Four Justices supported the man, William Osborne, but the court's majority said the decision whether to provide access to DNA tests is an issue for legislatures, not courts; 46 states and the Federal Government already mandate at least some access to DNA testing. "To suddenly constitutionalize this area would short-circuit what looks to be a prompt and considered legislative response," wrote Chief Justice John Roberts.

Since the advent of DNA testing in 1985, biological material (skin, hair, blood and other bodily fluids) has emerged as the most reliable physical evidence at a crime scene, particularly those involving sexual assaults. DNA, or deoxyribonucleic acid, contains the complex genetic blueprint that distinguishes each person. Forensic testing can determine if distinctive patterns in the genetic material found at a crime scene matches the DNA in a potential perpetrator with better than 99% accuracy. In 1987, Florida rapist Tommie Lee Andrews became the first person in the U.S. to be convicted as a result of DNA evidence; he was sentenced to 22 years behind bars. The next year, a Virginia killer dubbed the "South Side Strangler" was sentenced to death after DNA linked him to several rapes and murders around Richmond. DNA is also responsible for snaring Gary Ridgway, the infamous "Green River Killer" of Washington State, responsible for a string of murders around Seattle in the 1980s and '90s. After being implicated by genetic testing, Ridgway pleaded guilty and was sentenced to 48 consecutive life sentences. Law-enforcement agencies around the world are assembling DNA databases, which have yielded matches that investigators may otherwise have missed. The FBI now has DNA records on more than 5 million convicted offenders, and sex offenders in all 50 states are required to submit DNA samples to law enforcement.

In the early days of DNA testing, juries confronted with the novel technology sometimes hesitated to convict based on genetic evidence — witness the O.J. Simpson trial in 1995, when the ex–football star was acquitted, in part as a result of doubts about the reliability of evidence based on blood found at the murder scene. But analysts say those doubts have eased as scientific know-how improves and the public becomes more familiar with the practice through TV and movies. (One example of its ubiquity: a toy DNA lab based on the CSI TV series is available at Amazon.com.) Authorities say new techniques allow them to successfully analyze ever shrinking quantities of DNA — including from steering wheels and other items a criminal may have only briefly touched.

It's not just prosecutors and police who have embraced DNA testing. While genetic matches are extremely reliable in fingering criminals, they're virtually foolproof in exonerating the innocent. Some 240 convictions have been overturned in 33 states and the District of Columbia, according to the Innocence Project, a nonprofit advocacy group that works to free the wrongly convicted. Seventeen people have been released from death row after DNA evidence cleared them. Scott Fappiano, who spent more than 20 years in prison for the 1983 rape of a New York City woman, walked free in 2006 after testing showed he couldn't have been the attacker. "I just kept waiting," he said as he was released. "I'm just happy that it's over."

As accuracy rises and costs drop, DNA analysis is becoming increasingly widespread. It's familiar to daytime-TV fans as the leading method to determine paternity; do-it-yourself tests are now sold at drugstores. Footballs used in the Super Bowl are marked with DNA to prevent counterfeiting; officials say there's just a 1 in 33 trillion chance of getting the pigskins' genetic sequence right. In recent years, DNA evidence has also been instrumental in identifying human remains. Authorities established a massive genetic database following the Sept. 11 attacks, and DNA science helped give closure to the relatives of victims of Argentina's "dirty war," the bloody crackdown by military rulers in the late 1970s and early '80s. Among them is Hugo Omar Argente, whose brother Jorge was a victim of a 1976 dynamite blast. "They called me on the phone and said the test results had identified him," he told a reporter. "I just cried and cried."