For all the advancements in forensic technology over the past two decades, some areas continue to lag. Current shoeprint analysis techniques are still relatively old-fashioned and provide little information. Now, two British scientists have devised a new method that uses patterns of wear on the shoe’s sole to identify the wearer. They described their technique in the journal Scientific Reports last week.
Today, most shoeprint analysis can provide police with just two types of information: the type of shoe and its size. But the marks left behind by a suspect fleeing the scene or a missing person have much more information to offer. The trick is accessing it.
“There are only a finite number of shoe types in circulation and only a small subset of these are found at crime scenes (this is particularly true in the UK),” the authors write in the paper. “So how then, can we hope to use images of footwear that have been retrieved from a crime scene to differentiate between similar shoe types and identify an individual? The answer lies in the individual nature of the wear patterns that are exhibited by shoes worn by different people.”
The authors cite a 2002 study involving U.S. Marines. The research showed that although the soldiers wore the same shoes, the soles of their boots were different. Each person walked differently, thereby creating a unique pattern of wear. These patterns are not as identifiable as fingerprints, the current study authors say, but they could be used to link a suspect to a particular location.
Capturing those wear patterns requires more advanced techniques than are currently in use. But advanced doesn’t have to mean expensive. The authors assembled a scanner-like setup using just a pane of glass on a platform, strips of LED lights, black tape, and web cameras. For the study, participants stood on the light-lined platform, under which the researchers had placed the web cams. The participants were then asked to rock back and forth on their feet to simulate walking as the web cams recorded the impressions of their shoes against the glass. Afterwards, the recordings were translated into black-and-white images that could be compared to other shoeprints in a national database.
“There are potentially interesting uses for this type of pressure analysis in forensic science,” the authors write in the paper. “For example, this kind of approach could be used to determine how an individual distributes their weight through their shoe soles when they walk and/or run and hence determine roughly how fast they may have been moving when they deposited a shoe print. Combined measurements of contact area and pressure distributions could also be used to determine how hard an individual might have kicked a surface such as a door (during forced entry), or even possibly another person.”
While the apparatus is new, the technique itself builds on an existing process called Frustrated Total Internal Reflection (FTIR) imaging. Existing FTIR techniques looked at bare footprints, which might be helpful for crimes committed at nudist colonies, but not too many other places. The new shoeprint-reading technique has the potential to be of much broader use in police work.
“The low cost and ease of implementation of the technique make it particularly appealing for forensic applications,” co-author James Sharp said in a press release. “We are currently in the process of working with local police forensic laboratories and the Home Office to try to develop this work further.”