Police hunting a serial rapist in the French city of Marseille have used DNA evidence to arrest two men—but are unable to say which is the culprit as the pair are identical twins.
Both brothers are being held without bail as investigators face having to run extensive tests costing up to a million euros to distinguish between the 24-year-olds’ genetic codes, which are so similar that normal DNA tests cannot tell them apart.
“It’s a rather rare case for the alleged perpetrators to be identical twins,” said Emmanuel Kiehl, the chief investigator in the case, speaking to French media.
“We must determine the exact role of each one,” he said, adding that current techniques available for identifying the differences between DNA of identical twins were “onerous,” costly, and rarely conducted in French labs.
Mr Kiehl said the victims—six women between the ages of 22 and 76—had formally identified their assailants from photos shown to them by police, but that they also could not tell the difference between the twins.
Both suspects, identified only as Yohan and Elwin, 24, denied accusations they raped and sexually assaulted the six women between September and January in the southern French coast city of Marseille.
The attacks increased rapidly at the beginning of the year, with three committed in a span of three weeks.
The 76-year-old woman was the first victim. After being injured by her attacker, she was forced to perform oral sex.
Each attack took place at night, with the suspect or suspects assaulting the victim while in the entrance hall or stairwell of a building. The assailants also took the victims’ mobile phones.
With the help of video footage, a traced telephone belonging to a victim, and positive identification from the victims, local police were led to one twin. Then they discovered he lived with his identical brother.
“The seriousness of the crimes necessitates that an expert genetic examination is now launched and financed,” said a source working on the case, speaking to the French daily Le Parisien.
Investigators are going through with plans to complete the “enormous” job of decoding the DNA of the suspects, then comparing it to DNA found at some of the crime scenes, which reportedly matches the twins’ “common DNA”.
Local newspaper La Provence reported that police were told it could cost up to one million euros (£845,900) for the necessary tests.
It quoted a DNA expert saying that only the smallest of differences exist in the DNAs of identical twins. “For a normal analysis we compare 400 base pairs,” the expert said, adding that with twins: “We would be looking at billions.”
Scientists have demonstrated that differences in the DNA of identical twins exist. However the process of decoding those differences is “expensive and not fully developed and remains confined to research laboratories,” said Catherine Bourgain, a specialist on the issue at the French National Institute of Health and Medical Research (Inserm), speaking to French media.
The twins were described as being of mixed minority and Caucasian origin. “They are real identical twins, nothing really distinguishes them, and they repeatedly use and lean on the fact that they are twins,” said another source on the case, speaking to Le Parisien.
The brothers have stuck to the same line of defence, and only one of the two positively identified himself in a video taken on a bus. One of the victims had identified her assailant as the man in the video.
Both twins are unemployed deliverymen, who live alone together in an apartment in the working-class Belle-de-Mai neighborhood in Marseille. They are said to often share mobile phones.