It sounds like science fiction: geographic profiling† Using geographic data – such as escape routes or the crime scene – to determine where a serial killer, serial rapist or pyromaniac is hiding. Yet Bert Adriaens, geographical profiler, can effortlessly cite dozens of examples where it worked. The Westland tire pick, the pyromaniac of ‘t Zandt; every simple question reminds him of a case he was involved in.
Despite the extensive business history, the police’s ‘Geographical Investigation Advisory Team’ has only three members. Bert Adriaens, who started in 2003, and Jan Winter and Cor Rademakers, who were trained by Adriaens and joined in 2018. Adriaens would like to expand: “It is necessary.”
Before geographical offender profiling existed as a separate investigative discipline, the spatial environment was already important in criminal investigations. Pins on maps were connected with a red thread, search areas were marked with circles. Criminologists developed the crime pattern theory: The scene of a crime is not arbitrarily chosen but carefully chosen.
Also, the distance decay Discovered: The further a serial offender is from home, the less known the environment and the less likely he or she is to commit a crime. A perpetrator does not commit his crimes too close to home, for fear of being recognized.
Geographical offender profiling gained momentum in the 1990s. Canadian criminologist Kim Rossmo developed a way to distance decay expressed as an algorithm. Crime scenes can be entered in a formula to calculate the most likely place of residence or residence of a criminal.
Rossmo tested his formula on files of known serial killers. The technique was found to be 77 percent effective. He recorded his formula in the computer program Rigel. That divides a map into a grid of two hundred by two hundred points and calculates from each point how big the chance is that a criminal lives there. Geographic profiling as a research technique was born.
“Some people think that we only enter data into the computer,” says Adriaens. But that’s not right. „The principle is rubbish in, rubbish out† If the data you enter is incorrect, Rigel is of no use to you. We first visit the crime scene. And I want to know more than what happened inside the barrier tape. Does the unsub show local knowledge? Which direction did he go? Why did he choose this exact spot for a rape? Can I link the crime to another crime?”
Then they check whether the software confirms the analysis, says Adriaens. “95 percent of the work is at the front. The software just confirms or refutes, and makes it visual.”
In addition: a geoprofile is an investigation technique, never hard evidence. “We locate where a perpetrator may be, so that other police techniques can be better used, such as telecom data, license plate cameras, patrols.”
When Adriaens started, geoprofiling was still relatively unknown within the Dutch police. Nowadays Adriaens, Winter and Rademakers are involved in more and more cases. Adriaens: “People who have worked with us always come back.”
Although two of the three geographic profilers fall under the criminal investigation service in Limburg – the third falls under the National Unit – they work like a flying bird within the police. They are asked for business or offer themselves. Word of mouth leads to more demand.
Geographic profiling was first only used for serial crimes, but now also for simple cases, such as missing persons. The algorithm is not used here, there is not enough data for that, but it comes down to experience and geographical knowledge. Jan Winter tells about a murder case, in which the police knew through camera images in which environment the body was probably left. They also knew that the unsub had bought cement. On that basis, the ‘geoteam’ had to point out “asap” where the body was probably dumped. It had been thrown off a bridge, they decided. That is risky, but the perpetrator probably chooses the easiest way. That same day, the body was found by sonar boat in a cement-filled suitcase.
Such a ‘quick blow’ – in which geographical investigation advice is requested in the short term – is becoming increasingly common, says Adriaens. “Also with cold cases we are asked more. In the Nicky Verstappen case, they asked us what the best area would be to take DNA.”
“We can do a lot more with geo,” says Adriaens. “With more geographic profilers we can assist sooner. And with an analyst course, we can train people to ask the right geographical questions in less complex cases.”
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It is not yet certain whether there will be an expansion, “but it is the ambition”, says Danny Frijters, sector head of the criminal investigation service in Limburg. This also requires a culture shift, he says. Traditionally, cases have been led by tactical detectives – who arrive at the crime scene, gather evidence, conduct wiretaps and determine which specialists are needed. „Like Vledder and De Kock from the TV series Baantjer”, explains Frijters. That has to change, he thinks. “Specialists should be involved earlier in business. This way we know from the start which investigative techniques are needed, and cases are solved more efficiently.” The geoprofilers must play a role in this.
The question is: is expanding the georesearch advisory team wise? Is that the best use of a limited budget? The police has been struggling with shortages for years: in personnel (about 1,400 full-time jobs) and in money†
Jasper J. van der Kemp, a criminologist who wrote his dissertation on refining geographic offender profiling, seems to be “very sensible. Geographic profiling is pre-eminently an investigation technique with which other resources can be used more efficiently. It can also be used to identify serial offenders earlier. The criminal investigation department sometimes wrongly sees things as singular, which means that resources are wasted.”
Van der Kemp is moderately positive about the culture change. “If specialists have to be involved sooner, more officers must be aware of all the different expertise within the police, and know which cases require them. That almost requires a change of the entire police organization.”
A version of this article also appeared in NRC on the morning of April 6, 2022