‘New’ DNA technology sheds light on cold cases

Unsolved murders are increasingly being given a second look as investigators realise a simple technique can turn tiny DNA samples into usable evidence

Copenhagen Police have reopened the case into the 1990 murder of 23-year-old prostitute Hanne With after they identified the DNA profile of a possible killer.

The police employed a technique that can enhance small samples of DNA. The technique is proving increasingly common in cold case investigations – so much so that at least 13 unsolved cases have been reopened after the use of the technique has brought about new useable DNA profiles of suspected assailants.

But while Mid- and West Zealand Police say they reopened six cases due to “new opportunities” to extract DNA material, Bo Thisted Simonsen, deputy head of the University of Copenhagen’s Department of Forensic Medicine, says the techniques aren’t new at all.

“I am actually surprised to hear that these techniques are apparently new, because they aren’t to me,” Simonsen told Jyllands-Posten newspaper. “The PCR (polymerase chain reaction) technique was first described in 1987.”

Simonsen said that what was happening instead was that the technique was increasing in popularity as a result of high profile cases where it was employed, such as last year’s case of the ‘Amager Attacker’.

“For several years now, we have been getting calls from investigators wanting use to have evidence re-examined, so in that sense it’s not new. But I could imagine that as one case is taken up again, it inspires others to do the same.”

This seems to be the case. Over the past week, it has been announced that at least 12 new cases have been opened by many of Denmark’s police forces.

“The technique for extracting DNA material has been improved so much that it has now become possible to extract useable DNA from even small quantities of saliva or other biological traces that a perpetrator may have left behind,” Ove Pedersen, head of criminal investigations at Mid- and West Zealand Police, told Jyllands-Posten newspaper.

This is because the PCR technique makes it possible to use only a tiny amount of DNA to create enough material to carry out viable tests.

“The enzyme, polymerase, allows us to copy the DNA,” Simonsen said. “You can start with an incredibly small amount of material that you can copy to end up with enough to analyse.”

What makes the technique so effective is that samples can now be taken without contaminating them.

“When we take a sample of biological evidence, we also take contaminants. These might be colourings from textiles or fabrics from the ground. But over the past few years we have developed techniques to extract DNA with less contamination,” Simonsen said.

But whether the clues from the old cases can be used to provide usable samples in 2012 depends on how the samples were stored. Strong sunlight, heat a moisture can all damage DNA fragments.

And, even if a reliable sample can be found after all these years, there is no guarantee that it will reveal who the perpetrator of the crime is.

“A DNA profile alone does not reveal the identity of a criminal,” Simonsen said. “If there is nothing to compare it with, it can lead nowhere. But if you have a suspect it can be a real help.”




  • In conversation with Conrad Molden: The man behind the mic

    In conversation with Conrad Molden: The man behind the mic

    He’s tickled our funny bone with countless wisecracks and clever wordplay, and in the process, made Denmark feel a little more personable to many expats. An international import himself, funny man Conrad Molden has successfully carved out a niche for himself on the Danish stand-up scene, but it’s taken a solid 13 years, much trial and error, and heaps of Danglish

  • Volunteer Night 2025: when volunteering rimes with integrating

    Volunteer Night 2025: when volunteering rimes with integrating

    On Wednesday, April 30, from 17:00 to 20:00, Studenterhuset will host Volunteer Night 2025, a free event organized by the organization International House Copenhagen, which goal is to ease the relocation process for newcomers in Denmark

  • The international who shaped Copenhagen

    The international who shaped Copenhagen

    Anna Maria Indrio is one of the most important architects in Denmark, having contributed to shaping Copenhagen into what it is today. Among her best-known projects are the extension of SMK and Arken, as well as the Natural History Museum and the Darwin Centre in London. She moved here 60 years ago, when “Copenhagen was gray and dormant. Predictions suggested it would become depopulated. But putting people at the center changed everything,” she said

  • Danish government passes amendment to increase citizenship fee by 50%

    Danish government passes amendment to increase citizenship fee by 50%

    Fees were raised to reflect processing costs and curb repeat applications, creating debate over whether the new charges erect barriers to political participation for internationals.

  • Internationals’ labour contributes 361 billion DKK to Denmark’s GDP, and it is growing strongly every year

    Internationals’ labour contributes 361 billion DKK to Denmark’s GDP, and it is growing strongly every year

    According to a report by the Danish Chamber of Commerce, internationals’ contribution is 12% of the country’s GDP. In 2023, it was 322 billion DKK, and in 2008, it was 136 billion DKK. “Internationals make a gigantic difference in our prosperity and welfare,” comments Morten Langager, the Director of Dansk Erhverv.

  • Inside Denmark’s innovation engine

    Inside Denmark’s innovation engine

    With half of its staff being international, the BioInnovation Institute reflects Denmark’s broader transformation into a global innovation hub. But can the country—and Europe—keep up the pace? “If reforms are made now, we can close the gap in ten years,” explains BII’s CEO

Connect Club is your gateway to a vibrant programme of events and an international community in Denmark.