In 2006, a teenage girl in the United Kingdom revealed to her mother that her father was molesting her. When her mother refused to believe it, the girl decided to set up a webcam, aimed at her bed, to run all night. At 4:30 am that very night, the camera – which had switched to infrared mode in the dark – caught an arm creeping under the bed covers.

When you look at the human body under infrared light, the deoxygenated blood in veins shows up as black lines, making them more visible. The prominent vein patterns caught on camera allowed forensics expert Sue Black to identify the father as the perpetrator.

“The reason [this case] came to us is that the Metropolitan Police really did not know what else they could do with it. We didn’t know either at the time, because we’d never done anything like it. But we did notice on these images that you can see these lines – and we thought, ‘What about comparing them with the father’s vein patterns?’” said Sue Black, a professor of anatomy and forensic anthropology at the University of Dundee and director of its Centre for Anatomy & Human Identification.

Black’s three-person team was the first – and, it seems, is still the only – group of forensic experts to use the unique markings on human hands to catch paedophiles. When offenders record themselves abusing a child, they tend to shield their face and other easily identifiable body parts, but often leave their hands and forearms visible.

“These are truly distressing images – [but it’s] the only way the police are going to be able to investigate and the courts are going to be able to do justice”

This means that something as minor as a misshapen freckle or recognisable scar can help police build a case. In 2009, Black helped break up Scotland’s biggest paedophile gang by identifying an oddly shaped lunula – the white crescent that forms at the base of the nail – on the finger of Neil Strachan, one of the ringleaders.

Black’s team works on about 30 cases a year, for “nearly all” UK police forces as well as Interpol, Europol, the FBI, the UK National Crime Agency and the Child Exploitation & Online Protection Centre. Black has also worked with the Norwegian and Australian police, and is in talks with law enforcement agencies in Portugal and Spain.

Police send evidence – typically in the form of images or videos – as well as photos of the suspect’s hands to Black, who compares them with her database of over 1,000 people’s hands and forearms. If she finds the markings on the suspect and abuser’s hands to be consistent – and distinct from the others in her database – the prosecution will use her evidence in court. Of the cases Black’s team has worked on since 2006, 82% of the accused changed their plea from not guilty to guilty.

“It saves a tremendous amount of money and clogs up less courtroom time,” said Black. “But what it also does is prevent the victims and the families of the victims from giving evidence in court, and to me that is the most important thing.” Saving a victim from testifying helps them avoid the trauma of reliving the incident in front of dozens of people – often among them, the perpetrator.

Building a database of hand markings

In the 2006 case, the father vehemently denied the alleged abuse, so Black had the police take photos of his hands and forearms to compare with the vein patterns caught on camera. Veins are more distinctive than fingerprints – they are unique to every individual, even in the case of identical twins. These were a distinct match.

Black testified as an expert witness for the prosecution, marking the first time in history that vein pattern analysis was entered into evidence in a UK court. But when the jury came back, Black was shocked to learn that the father was found not guilty.

“We have to be reasonable about the fact that the human being is not a static object – it’s something that changes over time”

“There weren’t any problems with the science. The jury simply did not believe the testimony of the young girl,” said Black. “For us, that was a bit of blow. But it was very clear that we had something here, and should be able to help the police and the courts. What we needed to do is some serious research.”

The first step was building a substantive database of people’s hands, forearms and other body parts that would lend a scientific basis to Black’s work. She could testify in court that the veins of the abuser and the suspect matched – but a defence team could argue that many people have matching veins, and members of the jury may believe it.

With a database filled with photos of hundreds of people’s hands, Black can demonstrate how unique each individual’s markings are: veins, birthmarks, moles, nails, skin creases and areas of pigmentation, such as liver spots or freckles, are among the many distinctions Black takes into account.

To begin populating the database, Black asked a 550-person emergency response team she was training in disaster victim identification in 2007 for permission to photograph them. “Almost all of them stripped down to their underwear and allowed us to photograph their hands, arms, feet and legs,” said Black. “It allowed us to develop a complex database that we could interrogate – which has at least doubled in size now.” The team continues to crowdsource images and recruit people to send photos.

The new frontier in catching child abusers

Child pornography is a fast-growing problem in the UK. According to the Internet Watch Foundation, there was a 417% increase in the number of websites containing sexualised images of children from 2014 to 2016. About 69% of victims were aged 10 or younger, and more than a third of all images involved rape or sexual torture.

One in every 20 UK kids has been sexually abused, and 90% of these victims will develop mental health issues by the time they are 18 years old.

With police struggling to keep up with the proliferation of child porn, Black’s data-backed hand analysis offers a new way to present evidence – particularly as, in the past, UK law enforcement has mishandled major investigations into paedophilia, like Operation Ore.

In the country’s largest ever computer crime sting, US law enforcement handed over the details of more than 7,000 Brits who allegedly paid for child pornography online. Under mounting pressure to act quickly, police rushed to raid properties without thoroughly vetting the evidence. It later emerged that just 1,000 of the UK’s 140,000 police officers were trained in the basics of handling digital evidence. As a result, a number of the 3,744 people arrested were victims of credit card fraud and identity theft – who had never purchased explicit images of children.

“Recording that physical contact allows them to relive the experience”

Black can’t take on every case the police brings her; the photos and videos must be of high enough calibre to identify features that are often subtle. When the team accepts a new case, they have the police take photos of suspects’ hands in same positions as shown in the evidence.

Once they receive the photos, Black marks up any distinctive features and compares the two, taking into account differences in image quality and how the body changes over time.

“Scars or marks may have faded or disappeared,” said Black. “We have to be reasonable about the fact that the human being is not a static object – it’s something that changes over time.”

It’s impossible to scientifically guarantee a match, and Black still needs to reach a critical mass of data to establish greater degrees of certainty and be able to communicate the likelihood of the match to the court. “That’s the next step we’re working on: is it one in a million likelihood, one in 100, or one in 10? We need to drastically increase the size of our database in order to do that,” said Black.

“They tend not to think about their hands as being identifiable. Most people don’t believe they will be caught”

Another challenge the team faces is having to view violent, disturbing videos around the clock. To deal with it, they take as clinical an approach as possible.

“Though these are truly distressing images, we also know that our job is to collect the evidence, analyse and present it. That’s the only way the police forces are going to be able to investigate it and the courts are going to be able to do justice,” said Black. Both the Metropolitan Police Service and Dundee University offer free counselling to the team, but no one has taken them up on it yet.

Despite her team’s strides in the field, Black is doubtful paedophiles will stop filming themselves abusing children.

“Recording that physical contact allows them to relive the experience. For a number of individuals, it’s a currency – so they will share those images with other like-minded people,” said Black. “They tend not to think about their hands as being identifiable. Most people don’t believe they will be caught.”

(Picture credit: Flickr/Aditya Doshi)

Jennifer Guay

jennifer.guay@apolitical.co