Arrests in Louvre Heist Show Power of DNA Databases in Solving Crimes

It took less than a week for the police to track down two of the suspects who they say broke into the Louvre and made off with eight of France’s historic crown jewels. A third person, a suspected accomplice, was tracked down on Wednesday.

In all three cases, DNA was an essential part of the search.

The chief prosecutor, Laure Beccuau, said the DNA of the two men who broke into the museum and snatched $100 million worth of jewelry was found on the window and on one of the two high-powered motor scooters the thieves used to get away.

The DNA of the accused accomplice was found on the bucket of the truck-mounted mechanical ladder that was used to raise two of the thieves to the second-floor balcony of the Louvre, Ms. Beccuau said in an interview with the radio station France Info.

While the spectacular heist may have seemed like an advertisement for the lack of security at European museums, the speed of tracking the suspects was testament to the power of DNA in police investigations in France.

It is also a sign of how sloppy the thieves were in the end, after pulling off what seemed like a well-planned robbery in one of the world’s most famous museums in broad daylight. Among the objects they left behind in their haste to evade the police and security guards were a glove, a crown that they dropped, and the truck with the mechanical ladder, which they had tried unsuccessfully to set on fire.

Investigators have processed 150 forensic samples related to the crime, from the scene and from objects the thieves left behind. All three people who were arrested already had their DNA on file because of their criminal histories, mostly for theft.

“I am convinced that we would not have found these people if the DNA that was found at this theft hadn’t matched with this database,” said Gaëtan Poitevin, a criminal lawyer in Marseille whose master’s thesis was on France’s DNA database.

How does the DNA database work?

France’s database, the National Automated Genetic Fingerprint File, had 4.4 million DNA profiles at the end of last year. Those profiles have been collected over almost three decades from people suspected or convicted of crimes, as well as people killed in natural disasters.

It has become a staple of police investigations, with forensic investigators collecting bits of saliva, sweat, hair, skin, semen and blood, then sending them to be sequenced at public and certified private labs. The labs send the results to be compared to the contents of the enormous database, looking for exact matches.

“In just a few hours now, we can have a positive DNA result,” said Olivier Halnais, the head of the national union of forensic police officers.

How did France’s DNA database start?

France began its DNA database in 1998, after the serial killer Guy Georges, known as the “Eastern Paris killer” was finally arrested.

Mr. Georges had been imprisoned for assaulting a woman with a weapon, and the police collected his DNA. But France had no centralized database at the time, so officers were unable to check his DNA against that found at the scenes of five murders of women who had also been raped.

Initially, the database contained only the DNA of sexual offenders. But, over the next five years, it grew to include people convicted — or merely suspected — of a much wider range of crimes, including murder, terrorism, drug trafficking, assault, theft and property damage.

The process of being removed from the DNA database is so onerous that few pursue it, Mr. Poitevin said. Those who refuse to give a DNA sample face at least a year in prison and a fine of at least 15,000 euros, almost $17,400.

From 2018 to 2022, an average of 680 people a year were convicted of refusing to provide DNA — less than one percent of people charged each year, according to the Justice Ministry.

“Among my clients, absolutely zero refuse, because for them, it’s an admission of guilt,” said Mr. Poitevin.

As a result, the database has continued to grow. And French investigators can check the collected DNA against more than 30 other European national DNA databases, as well as others including one kept by the United States.

The database and cold cases

While the databank is used regularly for basic investigations, it has proved particularly useful in cold cases.

Investigators said DNA linked Dominique Pelicot, who was convicted last year of drugging his wife, Gisele, and inviting dozens of men to rape her, to an attempted rape committed more than two decades earlier. The 1999 attempted rape case had been dormant for years until the police arrested Mr. Pelicot in 2020, collected his DNA sample and ran it through the database, matching it to long-held samples collected at the crime scene. (Mr. Pelicot has been indicted in the attempted rape.)

Such searches for direct family members are much more time-consuming and used only for serious crimes like murder or rape, said Joëlle Vailly, a sociologist who has studied how the French judicial system uses DNA.

How is France’s system different than the U.S. one?

The French system is very similar to the American one, called the Combined DNA Index System, which contains more than 24.9 million DNA profiles of convicted offenders and those who have been arrested, as well as 1.4 million crime scene DNA profiles.

In recent years, American law enforcement agencies have also used consumer genealogy databases, including GEDmatch or FamilyTreeDNA, which are used by millions of people with no criminal record to find distant relatives or trace their ancestry.

These commercial databases offer police a pool of partial DNA matches that they then narrow using other techniques.

The practice of using commercial databases gained renown in 2018, when detectives used one to identify a serial killer known as the Golden State Killer.

In 2022, a Canadian researcher counted more than 800 cases in which forensic genetic genealogy was used in the United States.

Three American states have passed legislation to regulate the practice, said Natalie Ram, a law professor at the University of Maryland.

Private consumer genetics companies are banned in France, in good part because the practice of tracing one’s ancestry is sensitive, Ms. Vailly said, given the country’s history. The Jewish ancestry of many French citizens was used to send them to death camps during World War II.

Last month, France’s justice minister, Gérald Darmanin, said he planned to introduce legislation to allow investigators of serious crimes that have remained unsolved for more than 18 months to access data from private foreign companies, mainly American ones, specializing in genealogical testing.

While some lawyers specializing in cold cases lauded the announcement, others called the idea hypocritical and dangerous, since such companies are outlawed in France.

Ms. Vailly, the sociologist, said she thought the practice of using forensic genetic genealogy infringed on privacy rights, as one person using a consumer genetics service would essentially be offering up the DNA of whole families, not to mention future generations, to law enforcement.

“They become genetic suspects,” she said.

Ségolène Le Stradic and Ana Castelain contributed reporting from Paris.