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 identical twins?
Years later, they found an answer. A jury convicted Russell Marubbio, 54, of rape and abduction in late August after jurors were shown a new series of tests that found small mutations in Russell Marubbio’s and his twin brother’s DNA, distinguishing the two DNA profiles and conclusively ruling out the brother.
The Prince William County Commonwealth’s Attorney’s Office said the conviction was a milestone for the DNA testing technique, called somatic mutation analysis, that they used to secure the conviction.
“It’s not been successfully used in the courtroom before,” said Amy Ashworth, the Prince William County commonwealth’s attorney.
Peter Baskin, an attorney for Marubbio, declined to comment.
The woman, then 50, was working as an attendant at a Chevron gas station in Woodbridge in December 1987 and had stayed late to cover a co-worker’s shift one evening, she said in a 2023 court hearing.
She had just gone into the gas station bathroom, a separate building, when Marubbio pushed through the door and confronted her. Marubbio was 17 at the time, according to court records. The woman said he was holding a knife at his side.
After Marubbio raped her, he wrapped tape around her head and told her not to call for help for five minutes, the woman said. She stayed in the bathroom, afraid, as he ran away.
Police took her to a hospital and collected evidence with a rape kit. But there was no match for the DNA found at the scene, and the woman didn’t know her assailant. The case went unsolved for decades.
After Prince William County police reopened the investigation in 2019, a reexamination of the evidence led to Marubbio and his twin brother in Florida, according to the Commonwealth Attorney’s Office and court records. Florida authorities obtained cheek swabs from the brothers and confirmed their DNA matched the sample found at the crime scene in Woodbridge.
Efforts to reach Marubbio’s brother were unsuccessful.
Figuring out which brother had raped the woman required deeper testing. Investigators sent the brothers’ samples to Parabon, a company based in Reston, Virginia, that provides DNA testing for law enforcement, where scientists suggested using somatic mutation analysis to tell the twins apart.
The analysis works by finding small mutations in DNA that can occur as cells replicate and grow throughout one’s life, said Janet Cady, a bioinformatics scientist at Parabon.
“They happen in everyone, all the time,” she said, adding that finding them meant looking for “one position out of 3 billion” in the brothers’ otherwise identical genetic code.
Scientists more often test to find mutations that can cause cancer, Cady said. But for the brothers, these small changes that occur after a fertilized egg splits in the formation of identical twins would allow investigators to tell their DNA apart.
The science behind the testing is now well established, according to Cady and other expert testimony filed in court. But judges have previously expressed doubt. Prosecutors in Massachusetts, for instance, were rebuffed when they tried to admit evidence from DNA testing to distinguish between a man accused of several rapes in Boston in 2004 and his identical twin.
Suffolk County prosecutors said in 2014 that new DNA testing techniques would allow them to have no doubt in their case against Dwayne McNair, whose DNA matched evidence from the crime but who also had an identical twin. A Massachusetts Superior Court judge, however, ruled that the test was not admissible because it was unproven at the time. (McNair was convicted of rape using other evidence, according to the Suffolk County District Attorney’s Office).
Marubbio’s case was the first in the country where DNA testing evidence of this kind has been successfully admitted to distinguish between identical twins, according to court documents and the Prince William County Commonwealth’s Attorney’s Office.
Ashworth, the Prince William County commonwealth’s attorney, told The Washington Post it “absolutely” gave her pause to pursue a case based on a new DNA testing technique. But she ultimately likened it to previous advances in forensic sciences – such as fingerprinting, or the earliest DNA tests – that transformed previous criminal cases.
“Eventually the science evolves and the rules of evidence adapt,” Ashworth said.
Marubbio is set to be sentenced in November.
The woman, now 88, no longer lives in Virginia but testified in court hearings and was present for Marubbio’s trial, according to court records. Her family did not respond to a request for comment.
She “was very happy about the result,” Ashworth said. “She’s appreciative of all the work.”