Blood, Semen Tests May Replace Fingerprints
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 U.S. cases, a biochemist with the firm doing the analysis said recently.
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 added that his firm in Elmsford, N.Y., is to begin in February training police crime labs in the new technique.
Until recent months, Lifecodes was the only firm offering the service.
Admissible Evidence
Shaler said members 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 there has been some resistance from judges as well as juries.
“Juries have a very difficult time relating to scientific evidence,” Shaler said. “It’s very technical.”
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.
Variety of Cases
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 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. 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 grill 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 from March, 1986, to 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 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 working with bloodstains and a 74% success rate 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,” Shaler said, speaking at the American Assn. for Clinical Chemistry conference at the 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 with 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 with a stain found on a vacuum cleaner. But Shaler said the Oklahoma jury acquitted the defendant after concluding that he may have been in the house but had not necessarily committed the murder.
Most of the cases have yet to come to trial, Shaler said. Some of them never will. In one New York case, he said, the district attorney dropped the case after the defense hired Lifecodes and found the suspect’s DNA did not match that of the sample from the crime.
Lifecodes, which Shaler said was founded in 1982 to apply DNA probe technology to such things as cancer diagnosis and paternity testing, intends in February to begin training police laboratories in several states in the forensic techniques it is pioneering.
