Crime Library: Criminal Minds and Methods

All about the DNA Revolution

DNA in Court

After the initial success with DNA typing in England, Lifecodes began to develop the technology in the U.S. In 1987, Florida's Assistant State's Attorney, Tim Berry, contacted forensic director Michael Baird about a serial rapist case that was going to court. He wondered about the possibility of bringing in DNA identification as evidence. This was to be the first case to admit DNA testimony into the trial.

It began in May of 1986 when a man entered the Orlando apartment of Nancy Hodge and raped her at knifepoint. Grabbing her purse, he left. During the succeeding months, he raped more women, taking care to keep them from seeing him, and on his way out he always took something that belonged to them. In six months, he had raped more than twenty-three women, and he proved to be maddeningly elusive. However, he had made one mistake: He left behind two fingerprints on a window screen. When another woman eventually called him in as a prowler, his prints were matched to those from the window screen and they had their man: Tommie Lee Andrews.

Although his blood group matched semen samples taken from several of the victims, and the single victim who had caught a glimpse of him had made a positive identification, proving him to be a serial rapist would be difficult. There was too much potential in each of the other cases for reasonable doubt.

Blood samples from Andrews and semen samples from the rapist were sent to Lifecodes. Within two months the results were confirmed: the bar codes were too highly consistent for the semen in the rapes to be from anyone other than Andrews. The odds were stacked against it.

Nevertheless, DNA testing had not yet been accepted into court and before it could be used, it had to go through a pretrial hearing. Any time new scientific technology is introduced as testimony, it must pass certain tests of acceptability in the scientific community. That way the courts can avoid admitting evidence based on whim or junk science. DNA analysis had to prove to be scientifically sound in method, theory, and interpretation, and positively reviewed by peers. The hearing was long and complex, but finally the judge allowed the evidence into the case. However, the prosecutor made a misstep by stating impressive odds that he could not substantiate, and the jury was hung. Andrews was then tried on the second rape charge and convicted. Months later, the first rape charge was retried and the DNA evidence was brought in with more clarity and power. After that trial, Andrews' prison sentence stretched from his initial 22 years for rape to 115 years for serial rape.

From there, DNA gained increasing acceptance in the courts, although challenges were aimed at the way samples were interpreted or at shoddy handling of specimen evidence, such as happened in the Simpson trial. Because many different things can happen between the collection of a sample and the final interpretation, to ensure high standards, DNA testimony was reviewed on a case-by-case basis.

"When first introduced," says Keith Inman, "DNA faced few challenges from attorneys or the courts. That shifted dramatically in a New York case, People v. Castro, where the technology was challenged for the first time."

This 1989 decision by the New York Supreme Court was based on a pretrial hearing that lasted three months. Joseph Castro was accused of murdering his neighbor and her two-year-old daughter, and a bloodstain on his watch was analyzed for DNA codes. The court looked closely at both the DNA theory and the identification procedures, and held that the relevant scientific community generally accepted them. In essence, the testing could be used to show that the blood on the watch was not Castro's (exclusion), but could not be used to claim that the blood was from one of the victims (inclusion).

"There followed several years of hearings and decisions," Inman continues, "that culminated in the acceptance of the original protocols. With the adoption of new technologies by laboratories across the country, we are seeing challenges to these new advances, and a few courts are holding that the new protocols have not been tested enough to be assured of their reliability. However, the vast majority of courts are admitting the newer technologies. And there will always be the argument of the meaning of a match, that is, the statistical significance of finding that a reference [suspect] and an evidence item [specimen] share the same tested DNA types."

While some people worry that admitting DNA evidence into court may make genetic profiling into a tool for accusation—perhaps someone may have an "aggressive gene" and thereby be more likely to have committed a crime—for now it seems clear that the DNA revolution is far more beneficial than dangerous to criminal procedures.