Prosecutors have new DNA testing for twins

PAA New cutting-edge DNA tests can identify genetic mutations to differentiate between identical twins.

US prosecutors say they have a new tool to persuade jurors in cases involving twins: cutting-edge DNA testing that can identify genetic mutations to differentiate between identical siblings.

Boston prosecutors re-indicted a rape suspect earlier this month after receiving new DNA test results they say pointed to him but ruled out his twin in two rape cases in 2004.

Dwayne McNair, of Dedham, pleaded not guilty on Monday and is being held on $US500,000 ($A540,980) bail.

Boston prosecutors had a similar case a decade ago. Other cases have popped up in other parts of the US, showing the challenges of prosecuting a twin.

Standard DNA testing has not been able to differentiate between identical twins because they come from a single fertilised egg.

"The science behind this testing has been used in research, in paternity tests and in a variety of other capacities," said Jake Wark, a spokesman for Suffolk District Attorney Daniel Conley, whose office is now prosecuting McNair.

"The forensic application is novel, but it's supported by a widely accepted scientific foundation," Wark said.

McNair was scheduled to go on trial last April. But after prosecutors heard about the new DNA test done by a German company, Eurofins Scientific, they decided to temporarily withdraw the charges against McNair so they could get a new round of testing done on DNA taken from a condom used in one of the rapes. Eurofins says it has been able to identify genetic mutations to differentiate between twins.

Prosecutors re-indicted McNair earlier this month after the new test results pointed to McNair and ruled out his twin brother, Wark said.

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Prosecutors have new DNA testing for twins