Identical twins have identical DNA, right? Not exactly — not when you dive deep.

For the first time in the U.S., an identical twin has been convicted of a crime based on DNA analysis.

On August 21, a jury found Russell Marubbio, 54, guilty of a sexual assault that occurred in Woodbridge, Virginia, in 1987.

Identical twins have the same DNA – almost. There are sometimes a few cells that split and evolve differently.

“On average, twins will have eight of those types of differences across the whole 3 billion bases” of the genome, said Ellen Greytak, the director of bioinformatics at Parabon.

–Identical twin convicted based on DNA differences in first US case of its kind, The Guardian

I dove into the science of DNA and the rapid changes happening in the world of forensic genetic genealogy in a story about the Marubbio case for the Guardian this week.

But I wanted to share here more information I’ve learned about the case.

The hunt for genealogical records

The chief genealogist for Parabon, CeCe Moore, also discovered other clues pointing to Russell Marubbio over his twin brother. For instance:

• The assailant wore a letterman jacket with an “88” pin; Russell graduated in 1988, while his brother graduated in 1989.
• The assailant had a crew cut; according to yearbook photos, Russell had short hair while his brother’s hair was long.

These were among the 102 items entered into evidence for the trial.

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Obtaining DNA from suspects

Once a suspect (or suspects) are identified through investigative genetic genealogy work like this, police may arrest the suspect in order to obtain cheek swabs to compare that sample against DNA evidence left at the crime scene.

There’s a reason police detain suspects first instead of asking for samples: some suspects commit suicide before giving a sample, Moore told me.

In the Marubbio case, there were search warrants issued to obtain DNA samples of both twins.

Closure for the survivor

Finally, and perhaps most importantly:

The woman whom Marubbio assaulted is now in her late eighties. After nearly four decades of not knowing who attacked her, now she has an avenue for closure.

“She was grateful for all of the work that went into this trial and happy with the results,” Amy Ashworth, the commonwealth’s attorney for Prince William County, Virginia, told me.

Have a tip or suggestion for what I should cover? Get in touch securely via email (melodyschreiber@pm.me) or Signal (melodyschreiber.06).

Top image: Petra B. Fritz