A minute and a half: that's how long it took before DNA expert Arnoud Kal, with a beating heart, realized that Jos B.'s DNA profile matched the traces on Nicky Verstappen's body.

The substantive treatment of the case will start on Monday.

With NU.nl, Kal looks back on the breakthrough that started it all.

The Netherlands Forensic Institute (NFI) often had breakthroughs in long unsolved investigations.

Milica van Doorn, Marianne Vaatstra: these issues resulted in a breakthrough in the laboratories of the Biological Traces department, where Kal works with about 120 colleagues.

Everyone had hoped that the cold case Nicky Verstappen would also be added to this list, but it was not assumed.

In February 2018, thousands of men were asked to donate their DNA to compare it with traces found on eleven-year-old Nicky;

a so-called DNA relationship test.

"In the beginning colleagues always asked if there was already a match. I kept having to say no", Kal says about this period.

After a while, most of them stopped asking.

And then suddenly the day came.

On June 8, 2018, Kal is not looking at a profile from the DNA kinship investigation, but a profile that the police obtained in the home of a missing person.

This 55-year-old man from Simpelveld came to the fore in the investigation because he lived in the area at the time of the crime and did not want to give up DNA voluntarily.

Twice the officers stood at his door in vain.

When his family reports him missing, the police are given the opportunity to remove personal items containing DNA from his home and give it to the NFI.

"It took me about a minute and a half before I realized it was a match," Kal says.

"My heart was beating faster and faster."

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Profile Jos B., suspect in Nicky Verstappen case

'Information was not allowed to reach Jos B.'

The DNA expert quickly calls in a second pair of eyes, because "you won't leave something like that for a minute".

This second pair of eyes confirms what Kal already thought: it's a match.

The case officer at the Public Prosecution Service (OM) is quickly informed of this.

"And he was very surprised", Kal recalls.

But it will stop there for the time being.

"On the one hand, you would like to make such a big announcement. But on the other hand, the information should not reach the person himself. He will soon be doing something to himself," said Kal.

There was also the fear that B., who was still missing, would catch the plane to a distant place.

"We are always very careful, but in this case that was especially important."

The first match therefore did not come from the DNA relationship research, which specifically looks at the Y chromosome.

Every healthy human has 23 pairs of chromosomes, one of which (the Y chromosome) is passed from father to son almost unaltered for generations.

In this way, it can be determined whether the men who voluntarily donated DNA are possibly related to the person who left the DNA at the crime scene.

The net can close without the perpetrator having to give up DNA himself.

But it cannot be used for every case.

This depends, for example, on whether (usable) DNA material has been found at the crime scene.

"And DNA kinship research on this scale is of course a great appeal to volunteers who are innocent themselves. You ask the most personal thing they have from them," adds Kal.

“Even NFI director did not know about DNA match” DNA expert Arnoud Kal

Even NFI director not aware of match

While it is

business as usual

for the rest of the NFI employees

, a small group of the experts is silently working on a double check.

"It is second nature for NFI people to do extra checks and be as certain as possible," says Kal.

Immediately after that first match, DNA was received from two male family members of B. This again shows a confirmatory result: matching the Y-profiles.

For months, only directly involved NFI specialists knew about the match.

"So not the team managers, even the director of the NFI did not know," says the DNA expert.

It was a period of telling half-truths to anyone who inquired about the matter.

"We are still working on the investigation," said Kal, for example.

Which of course was technically correct.

Even his own wife only found out during the press conference.

"Just like the rest of the Netherlands. That is sometimes difficult, but at the same time she is also used to something. Although it must have been strange for her that I worked the evening before the press conference and slept in a hotel."

Arnoud Kal during one of his interviews about his work.

(Photo: ANP)

No champagne bottle uncorked

When asked whether he uncorked the champagne bottle or at least bought himself a pie after finding the match, Kal is clear: no.

"Such a match is special, but at the same time also the start of a whole new phase. Especially for the next of kin, who still have many questions."

Celebrating would be inappropriate at that time, the expert explains.

In addition: B. was still not arrested.

That happened a few days after the press conference, in Spain.

"Of course you hope for a match and that the police can immediately pick him up in his home. On the other hand, the investigation has been running for a long time and we have had so many unexpected events," the DNA expert nuances.

"Such as suspects who turned out not to be a match. The aim was therefore mainly to try to find information with which the investigation team could continue."

Jos B. during an earlier session.

(Drawing: Adrien Stanziani)

Is DNA match also offender evidence?

The question that will be central to the trial is whether the DNA trace shows that B. is guilty of the abuse and killing of eleven-year-old Nicky.

In any case, Kal will not comment on this.

Gerald Roethof, Jos B.'s lawyer, argues that the DNA match does not show that his client is guilty.

For example, it is not about semen or blood, as you would expect in a sex case, but about dander and hair.

In any case, Kal will follow the lawsuit sideways to find out what significance the DNA test will have in the courtroom.

"When the case is completed and the judge has put the right person behind bars, it is very satisfying that I have been able to contribute to that."