- The Washington Times - Monday, November 3, 2003

MODESTO, Calif. (AP) — Defense attorneys in the Laci Peterson murder case yesterday challenged the type of DNA analysis conducted on a hair found in Scott Peterson’s boat, saying the technique is too unreliable to be used in court.

Prosecutors said the hair, found in a pair of pliers in the boat, could be from Mr. Peterson’s wife, Laci, the mother-to-be who disappeared in December. An FBI crime lab supervisor testified during the preliminary hearing last week that mitochondrial DNA from the hair matched a gene swab taken earlier this year from Mrs. Peterson’s mother, Sharon Rocha.

Defense witness William Shields, a biology professor from the State University of New York at Syracuse, testified yesterday that while mitochondrial DNA testing can be useful, it is not as precise as other types of DNA testing.

Mitochondrial DNA cannot identify an individual specifically, but if compared with samples taken from a family member, it can show the statistical likelihood that a hair or other tissue came from a certain person.

Mr. Peterson, 31, told police he last saw his wife on the morning before Christmas as he left to go fishing near Berkeley. He said he returned to their Modesto home late that afternoon, shortly before family members reported Mrs. Peterson missing.

The bodies of Mrs. Peterson, 27, and her son washed ashore along the San Francisco Bay in April, about three miles from where her husband said he was fishing.

Mr. Peterson, a former fertilizer salesman, is charged with murder in the deaths of his wife and the baby boy she was carrying. The preliminary hearing is to determine if he will stand trial.

There is no evidence Mrs. Peterson was ever in the boat before her death, and prosecutors are expected to show that she did not even know about the vessel.

Mitochondrial DNA — a molecule that is much smaller than the more familiar nuclear DNA that is used to reveal a person’s genetic makeup — helped identify victims of the September 11 attacks on the World Trade Center. It can be extracted from hair and bones when little else remains of a body.

Peterson attorney Mark Geragos has branded mitochondrial DNA evidence unreliable.

Testifying for the defense, Mr. Shields said he was “appalled” at the sample size used by the FBI. Mr. Shields said mutations or contamination of mitochondrial DNA could skew results.

On cross-examination, Mr. Shields said he earns as much as 60 percent of his income from testifying for the defense in criminal trials and rarely works for prosecutors. He also said he had never extracted mitochondrial DNA for forensic purposes and is not a forensic scientist.

The hearing is being held because the technique has been used rarely in California courts. The prosecution must clear three hurdles to use the evidence. It must show that the technique is accepted by forensic scientists, that the witness is an expert in the technique, and that the testing and analysis were conducted properly.


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