Analysis Yields Genetic Makeup of Owner : Whodunit? Single Hair May Be Enough to Solve Crime

Scientists in California have uncovered genetic characteristics of people by analyzing a single hair strand, a significant step in using high technology to solve crimes, researchers say.

The technique can help show that a person was at a crime scene where a hair has been found, said Russell Higuchi of Cetus Corp., Emeryville, Calif.

He and Cetus colleague Henry Erlich described their work in the new issue of Nature magazine, along with George Sensabaugh and Cecilia von Beroldingen of UC Berkeley.

“It’s very exciting,” said John Hicks, deputy assistant director of the FBI laboratory in Washington.

The work focuses on DNA, or deoxyribonucleic acid, which forms tiny thread-like structures called chromosomes in every cell of the body. DNA consists of sequences of chemicals. Some sequences form genes, which control the activities of a cell.

Details of DNA sequences vary from person to person, and researchers have exploited that fact to help solve crimes by studying such “DNA fingerprints.”

Hair that has been ripped from the body, as in a struggle, often contains enough living tissue in its root area to permit conventional DNA analysis. But police more often recover hair that has simply fallen off a person at a crime scene, and it contains far less DNA, experts say.

Higuchi and colleagues overcame that problem by using a laboratory technique called polymerase chain reaction that creates 100 billion copies of a particular portion of DNA.

The ability to analyze a single hair is important, according to Hicks, because that is often all that is available at crime scenes. In addition, multiple hairs from a crime scene may have come from different people, said forensic hair expert Skip Palenik at McCrone Associates in Chicago.

At present, a shed hair is examined microscopically for its physical appearance, Palenik said. But different people can have similar-looking hairs, he said. The new report “represents a very important first step” toward firm identification of people from a shed hair.

In the Nature paper, researchers reported using a test to determine which of 21 versions of the “DQ alpha” gene is present in an individual. The gene plays a role in the disease-fighting immune system.

In tests of six people, researchers reported, a single shed hair correctly indicated which version of the gene each person had.

More recent tests show success rates of 40% to 70%, Higuchi said. The technique cannot now prove that a hair came from a particular person, but in combination with the microscope exam and other evidence its result can be seen as “very, very significant,” Hicks said.

Higuchi said the next research step is testing for more genetic characteristics to allow greater certainty in linking a hair to a particular person. If the hair and a person share characteristics that fewer than one in 1,000 people possess, he said, that would greatly help in making the link in court.