As of April this year, investigators in the Palmegroup have DNA-related relatives of one of those suspected of murdering Olof Palme, and the question now is whether they have had a hit. But how much DNA is needed to identify a killer?

- When we take things in, we always lose DNA in small amounts, we call it contact traces. It is enough to find DNA from 10 to 15 cells in order to obtain a full or at least a partial profile from a person.

In a dark and dry place

The murder happened 34 years ago, can the DNA traces really be left?

- Yes, there are cold cases that are older than you have been able to analyze DNA from before. The best thing is if the object has been in a dry and dark place and that not many people have touched it.

Now, unconfirmed sources say that the Palme investigation will present the murder weapon tomorrow. If so, what kind of clues might you have found?

  - Of course, I can only speculate about that, but it may be that blood from Olof Palme has been found on the weapon. If the weapon can be attached to a certain person, it becomes an important piece of evidence. But you may also have found contact marks on the weapon from the suspected killer. There may also be fingerprints from an offender on the weapon.

- In such cases, there is similar evidence found in the murder of Foreign Minister Anna Lindh. Both blood from Anna Lindh and contact traces from the murderer Mijailo Mijailović were found on a knife.

Dna on the coat

But others may have handled and taken the weapon that killed Olof Palme?

- Yes, but it may be less likely. This was a wanted weapon, and has probably been hidden.   

What else is there that may have been of interest to the investigation?

- There is information that the killer put his hand on Olof Palme's shoulder - but it may have only lasted a short while so there is probably not that much DNA. But if Olof Palme's outerwear is stored properly, it may still be worth trying to get a DNA profile.