Crime linkage systems can play a significant role in the apprehension of human trafficking gangs when scant traditional evidence exists. Computerized crime linkage systems are meant to assist police in determining whether crimes have been committed by theCrime linkage systems evolve to stop serial offenders

In 1999, a young orphaned girl was snatched from Haiti and smuggled into Miami where she was forced to work as a servant as much as 15 hours every day. She was never paid, was not allowed to go to school, and was occasionally beaten and subjected to other inhumane treatment. She finally managed to escape in 2005, according to the Federal Bureau of Investigation.

While it’s impossible to gauge covert activity with any accuracy, the United Nations estimated in 2008 that nearly 2.5 million people were being illegally trafficked into 137 countries, mostly for the purposes of commercial sexual exploitation or forced labor, most of them women and girls.

Despite police efforts to address and eradicate human trafficking, the crime remains rampant, even in the U.S. According to a 2003 federal estimate, some 18,000 to 20,000 human slaves are brought into the U.S. every year.

Crime linkage systems can play a significant role in the apprehension of human trafficking gangs when scant traditional evidence exists. Computerized crime linkage systems are meant to assist police in determining whether crimes have been committed by the same offender.

Tim Wedge, a forensic science professor at Defiance College, said that since much of the advertising for sexual trafficking occurs online and in public forums, crime linkage methods can be used to provide missing clues for investigators.

“Even if human traffickers move around, there should be unique identifiers in their online postings, such as characteristic word usages and digital images,” Wedge said.

Wedge said by using crime linkage methods it might be possible to isolate not only identifiers for individuals but identifiers linked, or likely to be linked, to specific activities as well, perhaps even distinguishing between involuntary sexual servitude and other services.

“With a well-designed and tested database of identifiers and a good Web crawler, millions of online ads could be searched, with likely offenders flagged for closer scrutiny and further investigation,” Wedge said.

Crime linkage systems can be traced back to the development of the Violent Criminal Apprehension Program by the FBI in 1985. ViCAP was designed to collect and correlate information about violent crimes. It remains the largest violent crime investigative repository in the U.S.

Other, more provincial, crime linkage systems exist, including the Homicide Investigation Tracking System in Washington state, the Homicide Evaluation and Assessment Tracking System in New Jersey, the Sex Crimes Analysis system in Iowa, and the Major Crime File used by the Royal Canadian Mounted Police. Crime linkage systems are also in use in Australia, Austria, Belgium, Czech Republic, France, Germany, Ireland, the Netherlands, New Zealand, Switzerland, and the United Kingdom.

The relative value of these systems centers on the data—how is it collected, who contributes, how is it validated, and what unique identifiers are used to link an object or individual to an event. The more contributors enlisted, the more useful data is aggregated. The more valid data collected, the more likely useful associations can be made.

“For a crime linkage system to be strong, you ideally want universal adoption by both users and contributors,” Wedge said. Wedge said data validation can be problematic, since the more people you have feeding the system, the more complicated validation becomes.

“Also, if the validation process is too difficult, contributors may opt out,” he said.

One big problem with crime linkage systems is that they themselves are rarely linked.

“While not due to actual competitiveness or ill intent, this results in competing databases, where you have two or more aggregations of the same or similar data targeting the same pool of likely users, controlled by different entities,” Wedge said. Wedge said before each entity reaches anything like universal adoption, a competing system may cultivate a large following of both contributors and users.

“Few contributors will want to duplicate their efforts and feed two or more entities, resulting in multiple, incomplete datasets,” he said. 

DNA Boost
Over the past several years, crime linkage has received a boost from DNA profiling. Many serial rapes and murders have been solved via DNA analysis.

Eric Hickey, of the California School of Forensic Studies, said that while profiling earned a bad reputation due to media exploitation of the term, the fact remains that profiling techniques are improving.

“We may choose to call it criminal investigative analysis or give it some other label to avoid stigma, but in truth crime linkage is profiling at its roots,” he said. Hickey said the key to profiling is the ability to integrate its various forms, such as crime scene profiling, geographic profiling, victim profiling, offender profiling, psychological autopsies, and paraphilia profiling.

“One cannot effectively improve crime linkage skills without first understanding what it is they are trying to link,” Hickey said. “We often don’t know what we don’t know.”

Hickey said being able to identify and create crime linkages in more precise and efficient ways requires a certain level of competency in profiling techniques. This is not armchair science but real integration of evidence-based knowledge through professional practice, he said. This is gradually being achieved through the collaborative efforts of academic researchers and law enforcement.

In efforts to codify and establish standards for criminal investigative analysis Hickey sees a need to create venues for certification that have commonly accepted rubrics and protocols for conducting criminal investigations.

“Eventually I anticipate we will see the establishment of national accreditation standards that will govern certification of those who are to become experts,” he said. “The more organized and collaborative the investigative community the more likely we will see improved techniques in crime linkage.”

One new international crime linkage network, scheduled for launch this spring, may also prove useful. The new network, called C-LINK (Crime Linkage International NetworK), will include police and academic partners from seven different countries.

C-LINK is the most recent example of the rapid growth in crime linkage methods over the last ten years.

“The C-LINK network will hopefully be an integral part of this development, as it will bring together key researchers and academics from around the world to address practical and theoretical problems,” said C-LINK network partner Matthew Tonkin, a forensic psychology lecturer in the UK at Birmingham City University. “Hopefully, the long-term future will see the development of statistical decision-support tools that can help crime and intelligence analysts to link crimes using behavioral information.”

Tonkin said crime linkage techniques are important for two reasons. First, they allow multiple crimes to be linked to the same offender, and evidence collected across several previously unlinked police investigations can be pooled.

“This may increase the quantity and quality of evidence available to police investigators, which will increase the chances of catching the person responsible and gaining a successful prosecution if the case reaches court,” he said.

Second, the actual process of linking crimes and combining previously separate police investigations can lead to a more streamlined and cost-effective way of using police resources, important at a time when law enforcement faces unprecedented levels of spending cuts.

“Behavioral crime linkage not only has the potential to improve the success of police investigations, but can also help to save money,” Tonkin said.

Douglas Page writes about forensic science and medicine from Pine Mountain, California.