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Brave new world for justice: DNA test for identical twins

WHILE THE advent of DNA testing has revolutionized some aspects of criminal justice, the system is still easily confounded by a not uncommon situation: a criminal suspect has an identical twin. And as methods of telling these twins apart emerge, the courts should be eager to test them out. But in Massachusetts, Superior Court Judge Christine McEvoy is blocking efforts by the Suffolk district attorney to seek state-of-the-art testing to determine whether a defendant or his twin brother was the source of DNA found after an alleged rape. While the judge may harbor doubts about the reliability of new tests, the scientific evidence appears compelling enough to warrant the 12-week continuance of the case requested by the prosecutors.

A suspect, Dwayne McNair, has been charged with raping two women at gunpoint in 2004, just eight days apart. One alleged victim, who was abducted while walking on a Roxbury street, had the presence of mind to retain a condom used by the perpetrator. That sample eventually identified McNair as a potential source of the DNA. But prosecutors couldn’t differentiate between that sample and one offered voluntarily by the suspect's identical twin brother, Dwight. It’s the same dilemma faced by law enforcement worldwide when confronted with cases involving one of a pair of twins who develop from a single fertilized egg.


But Suffolk prosecutors now believe that science has caught up to any criminal who tries to hide behind a genotype shared with an identical twin. Earlier this month, according to court documents, the trial prosecutor learned of a new procedure by a genomic testing company, Eurofins, proclaiming a “breakthrough in genetic discrimination between identical monozygotic twins.’’ A scholarly journal appeared to reinforce the company’s finding, as did a Harvard genetics professor who reviewed the paper at the prosecutor’s request.

McNair is scheduled to go on trial on April 29. But the DA wants a 12-week continuance, which will allow sufficient time for Eurofins to test his DNA sample. Judge McEvoy, however, has become impatient. In her April 16 ruling denying the request, she cited the novelty of proposed evidence “that has never been permitted in any court in the United States’’ and “is not generally accepted in the scientific community.’’


McEvoy is a highly respected jurist. But the best path to justice in this case would be for her to examine expert witnesses as to the reliability and accuracy of the new testing procedures. Simply stating that the next-generation sequencing test is not “generally accepted’’ by scientists does not make it so.

Whichever inconveniences arise from a delay of a few months in this case, they pale if compared with the public’s interest in seeing that the best available evidence of a defendant’s guilt — or innocence — is presented at trial.