An Interview with Dr. Peter de Knijff, a Pioneer in Forensic DNA

Leiden University’s Peter de Knijff humbly declines being called a guru, but, as a pioneer in forensic DNA, his contributions to the field have been plentiful.


Dr. de Knijff is a full professor in population genetics and evolutionary genetics at Leiden University Medical Center (LUMC), where he has lead the Forensic Laboratory for DNA Research since 1994. Among his favorite accomplishments, which he describes in more detail in the video below, is introducing the forensic DNA world to Y-chromosomal microsatellites for forensic genetic and population genetic applications, which he did in tandem with Professor Lutz Roewer and Professor Manfred Kayser.


In December 2015, Dr. de Knijff’s lab was the first forensic laboratory worldwide to receive formal ISO 17025 accreditation to use MPS for forensic case-work. In addition, he is actively involved in explaining forensic science to the general public, students and criminal justice professionals. He does this by means of popular lectures, courses, contributions to books and journals written in Dutch, newspaper articles and interviews for radio. He also regularly appears in court as a forensic DNA expert.


In the interview below, Lotte Downey of Promega, asks Dr. de Knijff how he first became involved in the field of forensic DNA, what it was like being involved in the first case where massively parallel sequencing was used to secure a criminal conviction in a criminal court, and what he foresees for the future of the technology.





Lotte: Hi, I’m Lotte Downey at Promega. [Speaking in Dutch] But, I know not a lot of people will understand Dutch, so we’re going to continue in English. Peter, you head up the forensic DNA research lab at the University of Leiden. Can you tell me a little bit about your job?


Peter: Yes, I started in that particular laboratory 25 years ago, because at that time, the Dutch politicians introduced a new law which gave suspects, who were forced to donate a blood sample for forensic DNA research, were given the independent right for a contrast piece. So, there was a need for a contrast piece laboratory in Holland. So, the Ministry of Justice shopped around to all the universities, and Leiden University agreed to house the contrast piece university, and they asked me if I would like to become the head of that particular laboratory. So, I thought about a month or so and then I agreed.


Lotte: Good, so what attracts you to forensics?


Peter: In the beginning, it was not so much forensics, but it was population genetics, because I knew that doing forensics also meant that you had to invest in population genetics, in order to read the data. And, I very much like all the statistics involved in population genetics. But, in the end, also I like the technological developments, and if there is any field that in science that technology has played a major role, it’s DNA research, in the general sense. And my lab is part of a very big, technology driven, human genetics department. It was already 25 years ago, and it still is. So, I’m just exactly where I want to be.


Lotte: Good. So, you’re talking about your love for technology and you’re technology driven. Would you agree with me that you’re being seen as the guru of Next Gen Sequencing in forensics?


Peter: Well I’m certainly one of the first people speaking about it, for already a long time now predicting in the end that it would become a major field, but as with all new technologies, especially forensics, many will fail to deliver, so you never know in advance if you start a new technology, whether it will be successful. But, as stubborn as I am, I think we can agree that it is now successful. So, we have an end product. We can do massively parallel sequencing in forensic casework very successfully. So, it took 10 years, but we do it now.


Lotte: Good! I would call you the guru of massively parallel sequencing in forensics. So, like you say, you’ve been a pioneer in it. You were the first one to present a case that used massively parallel sequencing in court. Can you tell me a little bit on how you got the court to accept this new technology?


Peter: You know, that’s not a problem, because we can only use technologies which are ISO 17025 accredited. When the court reads that this technology is accredited in Holland, they know that it has underwent rigid testing and quality assurance testing, so they know that it is reliable and useful. Nevertheless, they also need to be able to understand exactly what you are doing, and the major advantage of applying massively parallel sequencing to STRs is that the court system is used to working with STR variation. We just identified the STR variation in a different way. So, it is very close to their comfort zone. That is the reason why I deliberately choose to stay using STRs as the first example of massively parallel sequencing, because it is close to what judges think they understand. And that helps tremendously. So, it wasn’t challenged. Also, not by the defense.


Lotte: Really? That’s amazing. So, where do you… What role do you think and what impact do you think massively parallel sequencing will have in forensics in the next five years?


Peter: We will see a great change of laboratories using massively parallel sequencing in not necessarily routine technology, but in those stains where capillary simply fails to deliver results, where there is still enough DNA to be interrogated is where massively parallel sequencing can help you out. But I see the way we use massively parallel sequencing right now as an intermediate phase between capillary and just going for whole genome sequencing. Because I think that, in the end, is where we are going, but it is too far-fetched for most people right now in forensics. Not in clinical diagnostics, but in forensics it is.


Lotte: How long do you think it will take before it gets there in forensics?


Peter: Years, at least.


Lotte: So, I just want to switch gears for a little bit. What would you consider, from your standpoint, are your biggest accomplishments?


Peter: Well, three things. The first, getting Y-STRs successfully used in forensics, which is what I did in the late 90’s together with Manfred Kayser and Lutz Roewer, and now it is a routine tool, but we were the first. And now, later, developing a DNA isolation method which allows me to get DNA profiles out of cartilage, which were at that time, considered to be impossible to get DNA profiles from, but we can, and we introduced the technology, and finally now it is seen that it is delivering – also in the United States. Labs took over the technology which I developed. And, massively parallel sequencing is still the nicest thing, because that’s something that where I was involved in not only the lab work, but also the idea space. So, writing the scripts. Writing the software. And also being able to demonstrate, even in court, if necessary, what you are doing. And then to even be able to show every single read you get out of an experiment. That is something that we thought about very carefully when we started with everything, and we now have a full product, and it’s being used now, at least in Holland. And it will be slowly used now in other countries. I think that it will have, in the end, a major impact.


Lotte: Can you tell us a little bit about what you’re presenting at the meeting this week?


Peter: It’s very simple. I will explain very, very simply what massively parallel sequencing for short tandem repeats is. Most people probably already know it, basically. And I will present three different case examples, where I will show the comparative value in using MPS in cases where capillary couldn’t deliver the essential message. Meaning you could either exclude a suspect or include a suspect or make a choice between two equally likely suspects. So, that’s exactly what you can do with MPS, so that’s what I will show.


Lotte: I’m going to add one surprise question, and I’m stealing this question from my colleague who interviewed Walther Parson. So, she asked Walther, and I’m going to ask you. If you’re in a tree and you have a gun, and one bullet, and you see a lion, a pair of leopards, and (I’m just making this up) a tiger. Who are you going to shoot first?


Peter: The lion.


Lotte: Can you say why?


Peter: As a predator, I think that the lion is the most unpredictable. I understand cats, but lions have the capability of hiding their emotions, whereas leopards and tigers can’t. So, I would feel more safe among the leopards or tigers than a lion.


Lotte: Ok, that’s a great answer. Thank you so much for your time!