DNA Fingerprinting: A Powerful Law-Enforcement Tool with Serious Social Implications

DNA fingerprinting has been hailed by law-enforcement officials as the 20th century’s most important breakthrough in forensic science. They are eager to use the new technology to identify and prosecute violent criminals as well as to exonerate innocent persons who are suspects in criminal cases. Although DNA finger-printing has not yet been adequately tested in the courts, the State Attorney General of California recently proposed creating a computerized data base of genetic information on violent criminals. However, transferring DNA fingerprinting from the lab bench to the bar may not be as easy as it seems. The legal application of this new technology raises serious and controversial issues of interest to scientists and the general public. The term “DNA fingerprinting” was coined by geneticist Alec J. Jeffreys, University of Leicester, U. K., who developed the method in 1985. Several of Jeffreys’ “hot” papers were identified in a recent issue of The Scientist (January 23, 1989, p.12). Briefly described, Jeffreys’ method produces a complex pattern of bands from particular regions of the DNA molecule called minisatelIites. Experts claim that the patterns are as unique to an individual as his or her fingerprints. These individual-specific genetic fingerprints can be obtained from minute samples of blood, skin cells, semen, or even a single hair. The condition or age of these biological samples does not affect the ability of the method to produce DNA fingerprints. The specificity and flexibility of genetic fingerprinting make it an ideal tool for forensic investigations and criminal prosecutions. The legal application of DNA fingerprinting raises the interesting question of how scientific evidence is evaluated and ruled admissible in court. The first legal hurdle any new scientific technology must overcome is the so-called Kelly-Frye rule, a precedent established in 1923. The rule states that anew technique must be generally accepted as valid by a consensus of expert opinion before it can be used as evidence. But expert testimony on the complex genetic and statistical assumptions underlying DNA fingerprinting may confuse nonscientific judges, attorneys, and juries. As a result, they might reject the evidence