DNA Expert Testifies Evidence Points to Suspect in 1973 Rape by Trillion-to-1 Odds


An expert in criminal DNA analysis testified yesterday that the odds were one in a trillion or longer that Fletcher A. Worrell, a defendant in a Manhattan rape trial, was not the man whose DNA was recovered from underwear the victim wore on the day of the June 1973 assault.

The expert, Mary Quigg, a forensic biologist from the Manhattan chief medical examiner's office, took the stand for the prosecution in Mr. Worrell's trial for the rape of Kathleen Ham 32 years ago in an apartment in the Chelsea section of Manhattan. After Mr. Worrell's arrest last year, prosecutors found Ms. Ham's aqua green underpants stored deep in their cold case files.

Ms. Quigg's testimony left clear the difference that DNA testing has made in the case, which ended with a hung jury when Mr. Worrell was first tried in November 1974, before such tests existed. Ms. Ham was not able to identify Mr. Worrell, who went by the name of Clarence Williams in the first trial, as the man who attacked her because the assailant had pulled a sheet over her head.

Ms. Quigg walked the jury through the complex results of a comparison of DNA recovered from the panties in February 2005 to a DNA profile of Mr. Worrell completed two weeks later using skin cells from the inside of his mouth.

Examining the two DNA profiles broken down in 14 standard categories, Ms. Quigg said, there was a perfect match in 12 categories.

"You would need 166 planets Earth with six billion people on each planet to see another individual with this profile," Ms. Quigg said. Traces of Ms. Ham's DNA were also found on the underwear, Ms. Quigg said, but Mr. Worrell's DNA was a "much larger amount."

Mr. Worrell's defense lawyer, Michael F. Rubin, clashed with the justice, Bonnie G. Wittner of State Supreme Court in Manhattan, as he tried on cross-examination to undermine the reliability of Ms. Quigg's findings. He tried to show that if the medical examiner's laboratory had done a different kind of test on the DNA samples, the results might have shown mutations that would rule out Mr. Worrell, who is now 59.

But Ms. Quigg, at times appearing vexed by Mr. Rubin's interruptions, insisted that such mutations were "extremely rare, almost impossible." Justice Wittner became exasperated when Mr. Rubin questioned Ms. Quigg about two scientific articles from the mid-1990's about DNA testing.

"That's such a ridiculous question," Justice Wittner said, overruling one query from Mr Rubin. "I don't know what it means myself," she added.

"Judge, I don't like you testifying in court," Mr. Rubin shot back.

"Mr. Rubin, no comments, please," the justice responded, silencing him.

Ms. Quigg made it clear how recently DNA has become widely used in criminal prosecution. The first cases where it was used were in 1988, and standardized nationwide testing procedures were put in place only five years ago. Other testimony showed how drastically forensic methods in rape cases have changed since 1973.

Dr. Patricia M. Carey, the medical director of the emergency department at St. Luke's-Roosevelt Hospital Center, analyzed the report on the medical examination performed at the hospital on Ms. Ham, who was 26 at the time, about an hour after the attack on June 26, 1973.

A physician, identified in the report only as Dr. Finnerty, noted "superficial lacerations" on Ms. Ham's neck. But he added that Ms. Ham "seems rather calm at this time." Two hours later, a gynecologist, identified as Dr. Nagle, used a glass pipette to take a sample from Ms. Ham. Examined under a microscope, it tested negative for sperm. In the first trial the defense lawyer, George C. Sena, used the medical report to cast doubt on whether Ms. Ham had been violently assaulted.

Dr. Carey said the glass pipette was abandoned for testing when more extensive examinations, called rape kits, came into use in 1978. She also testified that it was not unusual for rape victims to appear cool.

She said the three knife cuts on Ms. Ham's neck were "a remarkable degree of physical assault" in a sex crime. Dr. Carey said that studies now show that 60 percent of rape victims have no physical injury.

Mr. Rubin's cross-examination of Dr. Carey lasted one minute.