In December 1987, a man burst into a gas station bathroom in Woodbridge, Virginia, shortly after a woman entered. He was carrying a knife. The man raped her, the woman said in a court hearing, and afterward tied duct tape around her head, covering her mouth and nose.

Then he ran away.

The case sat cold for decades until Prince William County detectives reopened it in 2019. They tested evidence gathered from the scene to try to identify the perpetrator through his DNA.

Authorities found a match. Then another one. The test pointed to two men in Florida who shared the same DNA profile, indicating they were identical twins.

It seemed like the woman’s case would again sputter to a halt as a result of a conundrum that has long stumped investigators: How can you distinguish between the DNA of

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