Instead of ancestors we try to track down family descendants

two girls and a boy. The boy became the prime suspect and was convicted of murder. It’s like putting together pieces of a jigsaw puzzle, reverse-engineering the identity of the suspect based on the family tree of people sharing DNA with him.

“Instead of going back in time to find longdeceased ancestors, we’re flipping the tree upside down and trying to find living descendants of those ancestors.”

The Talbott trial last year made legal history. It was the first jury conviction in the US based on genetic genealogy. He is now serving two life sentences for the killings.

Cece said: “You’re hoping your top match is going to be at least a third cousin and you can go back to a second greatgrandparent. If you’ve got a lot of really close genetic matches it’s obviously going to be a lot easier.”

Genetic genealogy is such a new science it isn’t taught at any university. Cece pioneered techniques as she went along after her interest began about 20 years ago.

“My niece was getting married, and I thought our family tree would make a great gift. I traced family members back to the Mayflower, to Norway and Finland. I was so engrossed I kept going.”

In 2018 Cece joined Parabon Nanolabs in Reston, Virginia, as their chief genetic genealogist, taking her research to law enforcement and quickly winning a reputation for cracking cases that were thought unsolvable

Cece’s TV series Genetic Detective is coming to Britain later this year.