In "Crime and the Millennium," his excellent introduction to the The Mammoth Book of True Crime(Carroll & Graf Publishers, 1998) Colin Wilson describes how DNA fingerprinting was discovered by a scientist named Alec Jeffries in September 1984, and the first high profile case solved because of it...
"D.N.A. forms ... the basic building blocks of life, and comes in long strings of molecules shaped like a double helix. Jeffreys isolated certain blocks of D.N.A., then mass-produced them, and learned to stain them with radioactivity. He then took an X-ray film of the 'block', and saw that it came out as a long column with black stripes against white backgrounds. This is the 'genetic fingerprint.' Next, he took samples of blood from whole families and set out to see if there was any family resemblance. There was -- a child's genetic fingerprint was a combination of those of his parents. Unlike real fingerprints, genetic fingerprints are not unique, but the odds of two unrelated people sharing one are about four million to one.
"In the late 1980's, there had been a long series of rapes in the Toronto suburb of Scarborough. Paul Bernardo came under suspicion because he resembled a composite sketch of the rapist, and a sample of his blood was taken. But he was one of more than 200 suspects, and when he heard nothing more, he assumed he was in the clear. It took nearly two years for the lab to process his sample and conclude that he was the Scarborough rapist. By then, he had murdered the two schoolgirls .... Bernardo was finally arrested and eventually sentenced to life imprisonment."
DNA is one of the most effective crime-solving tools available to law enforcement. A white paper on the Forensic Science Services (England and Wales) by Christopher H, Aplen, J.D. claims that the suspect identification rate for domestic burglary increases from 14 to 44 percent when DNA is available at the crime scene. Since a burglar can be expected to commit a good many crimes in a year's time, putting more of them behind bars using DNA would reduce the incidence of burglary.
One problem, though, is that the sheer amount of evidence requiring DNA testing has reached such high levels that backlogs at forensic labs have become chronic, and sometimes alarming. In 2002, federal, state and local labs in the United States reported a backlog of over 500,000 requests. When Howard Safir was New York City Police Commissioner he found 16,000 rape kits that had not been DNA tested due to lack of funding.
Reading this you might assume that since the advent of DNA fingerprinting, the percentage of rape cases in which the rapist was caught has increased. And since rapists normally commit the crime more than once, you might even think that rapes themselves might be in decline. Think again.
The FBI began DNA testing of rapists in 1989. A report by the Department of Justice almost a decade later estimated that at least 25% of all men convicted of rape in federal cases were innocent -- and perhaps as many as 40%. One reason for this had nothing to do with DNA, but rather with the fact that 98% of reported rapes are false accusations. The percentage is that high in part because only 5% of actual rapes are reported. The report states:
"FBI officials report that out of roughly 10,000 sexual assault cases since 1989, about 2,000 tests have been inconclusive (usually insufficient high molecular weight DNA to do testing), about 2,000 tests have excluded the primary suspect, and about 6,000 have "matched" or included the primary suspect.1 The fact that these percentages have remained constant for 7 years, and that the National Institute of Justice's informal survey of private laboratories reveals a strikingly similar 26-percent exclusion rate, strongly suggests that post-arrest and post-conviction DNA exonerations are tied to some strong, underlying systemic problems that generate erroneous accusations and convictions. [italics mine]" In 2005 the FBI reported that rapes had increased 5% since 2000, while the crime rate as a whole was down.
This leads us to one very important consequence of the widespread use of DNA testing. In February 2010, a Rochester, NY man who had served 33 years in prison after a rape conviction, became the 250th prisoner exonerated by DNA in the United States.
An issue that is currently in the news is whether the DNA fingerprint of every citizen should be taken and stored by the authorities. In the UK, every person charged with a recordable offense has his or her DNA placed in the National DNA Database -- and even those of people later found innocent are retained. Civil liberties organizations argue that this is an invasion of privacy; proponents claim it's a small price to pay for a safer society. The problem, of course, is that a mistake could be made; the one thing you can depend on a bureaucracy to do is screw up. The U.S. has its own DNA database these days, called CODIS, which currently contains over 4.2 million samples. Law enforcement and victims organizations are pushing for a DNA sample to be taken from every person arrested for a felony, and everyone detained by federal authorities. (The 2004 Justice for All Act of 2004 signed into law by President George W. Bush provided over $750 million to help in reducing backlogs, and expanded the criteria for taking samples from arrestees for inclusion in CODIS.)
Does DNA Testing Reduce Crime?