For over 20 years, the police have used blunt DNA tests that can only detect the closest relatives, such as a sibling, a child or a parent.

The DNA tests that are now sold online to private individuals provide more information than the police's old DNA tests. Thanks to the fact that individuals have started DNA testing, it is now possible to reveal relatives or even more distant relatives.

This new technology was used to solve several notable homicides in the United States a couple of years ago. A serial killer, the so-called Golden State Killer, was arrested after police uploaded his DNA profile to an American genealogy free site.

Undetected for 16 years

The arrest raised hopes of the police in Sweden being able to solve some of the almost 700 unresolved murders and deaths that are pending.

One of the most famous is the double murder in Linköping from 2004. Two people, a child and an adult woman, were stabbed to death by a perpetrator who stayed away for 16 years.

The police have collected over 40,000 documents in the largest investigation ever, after the Palm murder, and among other things have secured the perpetrator's DNA on the knife used.

Pilot project

In a pilot project, the DNA profile was downloaded, both in the US free site and at one of the private companies that sell tests to private individuals, and which is used by many Swedish genealogists.

And it was the latter search that yielded results.

- We got hundreds of matches, of which 10-15 were fairly close to relatives, says Peter Sjölund, Sweden's foremost expert on DNA genealogy who helped the police in the work.

"Right person"

Sjölund has used the names of the persons to search church books and other traditional sources. In this way he has been able to see how the different families are connected. All in all, he has tracked between 600 and 700 people back and forth throughout history,

- It took a lot of work. But in the end I was down to a single family, he says.

The research has now led to a person being arrested for the murder. The suspect's DNA will now be compared to the findings from the crime scene. Peter Sjölund believes that it is very unlikely that the track will lead wrong.

- I'm pretty sure they've found the right person, he says.

Can solve many crimes

According to Peter Sjölund, this is a method that could be used on a large scale, if the police choose to make the pilot project a standard method

- If you want to proceed on a broad front, then you need to hire more genealogists who have experience working with DNA, but I think it would lead to many more serious crimes being cleared up, he says.