A murder trial in France has raised unusual forensic challenges after investigators were unable to determine which of two identical twin brothers fired the weapon used in a double killing.
The 33-year-old brothers, identified only as Samuel and Jérémy Y, are among five defendants accused over the deaths of two men in 2020. The victims, Tidiane, 17, and Sofiane, 25, were shot dead in a cellar in Saint-Ouen, a suburb north of Paris, on September 14 that year.
Both twins are alleged to have helped plan the killings. However, DNA recovered from one of the firearms has complicated the case. Forensic experts confirmed the genetic material belongs to one of the brothers, but they cannot determine which one.
“Only their mother can tell them apart,” one investigator involved in the case said.
Identical twins share the same DNA because they develop when a single fertilised egg splits into two embryos. This makes it extremely difficult for standard forensic testing to distinguish between them.
Investigators believe the brothers may have deliberately exploited this similarity. According to police, they regularly swapped clothes, phones and identity documents, a practice that officers say may have been intended to obstruct identification.
A police commander told French newspaper Le Parisien: “They exchange clothes as well as phone lines and identity papers. For a very long time, they have used this twinship in their criminal career.”
The forensic specialist who examined the DNA evidence said only one person’s genetic material was present on the weapon, adding to the uncertainty over who pulled the trigger.
Although identical twins share virtually identical DNA, small genetic differences can arise from rare mutations over time. Detecting these variations requires highly specialised testing and is not part of routine forensic analysis.
The trial is ongoing and is expected to conclude in late February.
It is not the first time courts have faced difficulties when identical twins are involved in serious crimes. In the UK, twin brothers Kailum and Kieran Nightingale were convicted of manslaughter after killing a man during a failed drug deal, a case that also raised questions about the limits of DNA evidence.
