Chemists Told of Advances in ‘Genetic Fingerprinting’

A method of analyzing blood and semen for a “genetic fingerprint” that some predict will replace traditional fingerprinting in court cases has been used in recent months in more than 100 cases nationwide, a biochemist with the firm doing the analysis reported in San Diego.

Robert Shaler of Lifecodes Corp. told a conference of chemists that the technique for comparing the blood and semen samples from crime scenes with those of suspects or victims has proven so precise that in many cases the identification is 99.9% reliable.

“What we’ve done is made a qualitative leap in our abilities to identify the perpetrator of a crime, especially a sexual assault,” said Shaler, who said his firm in Elmsford, N.Y., is to begin training police crime labs in the new technique in February.

Until recent months, Lifecodes was the only firm offering the service.

Shaler said employees of his company have testified in criminal and civil cases in New York, Oklahoma, Florida, Virginia and Kentucky. He said the firm also withstood a challenge to the admissibility of its evidence in a special hearing in Florida.

But he said Friday that there has been some resistance from judges as well as juries.

“Juries have a very difficult time relating to scientific evidence. . . . It’s very technical,” Shaler said.

So-called DNA fingerprinting, developed by a British geneticist in 1985, entails extracting deoxyribonucleic acid from samples of blood, semen, hair, bone or tissue. DNA, found in the chromosomes of living beings, contains an individual’s unique genetic information.

The DNA is then analyzed and compared to DNA taken from a suspect in a criminal case or a man accused in a paternity case. If the patterns of bands produced by the analysis match, there is an extremely high probability that the DNA is from the same person, Shaler said.

The technique is applicable in homicide and assault cases in which a sample of the criminal’s blood was left behind, in paternity cases using the fetus’ blood or tissue, in hit-and-run cases using the victim’s blood or tissue, and in body identification.

Shaler said the system is most applicable in sexual assault cases because a very small amount of semen is needed. He said dried blood can be analyzed if the stain is at least as large as a dime or a quarter. Hair, bones, tissue and teeth can also be used.

In one murder case, in which the body had not been found, Lifecodes analyzed a fragment of brain tissue found on the grille of a car. In another, the firm studied dried blood found in the crevices of a watch.

Lifecodes examined 79 samples of blood, semen and tissue submitted by law enforcement agencies and defense lawyers between March, 1986, and August, 1987. The firm’s ability to analyze each sample was determined by its size and purity, Shaler said.

For example, there was insufficient DNA found in the samples in 21 of the the 40 sexual assault cases. Even so, Shaler said the success rate in sexual assault cases compares favorably to the more limited success rate of traditional methods.

He reported a 70% success rate in working with bloodstains and a 74% success rate in working with tissue. Shaler said the success rate in sexual assault cases has risen since August, as the total number of cases handled by the firm has risen to more than 100.

“The use (of the technique) has a great deal of potential,” said Shaler, speaking at the American Assn. for Clinical Chemistry conference at the San Diego Hilton. “We’ve been able to show that, in real-life cases, we’ve been able to get some spectacular results.”

Shaler said the outcomes of the court cases so far have varied.

One rape case in Florida, in which the firm linked a semen sample to the defendant, ended with a hung jury. Shaler said the defense called two witnesses who testified that the defendant was elsewhere at the time of the crime.

In a murder case, Lifecodes linked the defendant’s blood to a stain found on a vacuum cleaner. But Shaler said the Oklahoma jury acquitted the defendant after concluding that he might have been in the house but had not necessarily committed the murder.