Footwear evidence and 3D laser scanning

Imprinted in sand, moulded in dirt, or stamped on the floor—footprints discovered at crime scenes can provide evidence for forensics teams who play a vital game of whodunit. In a two-dimensional form, the evidence can be flawed at best. With the use of a FARO scan arm, laser points, and CloudCompare, these simple prints become three-dimensional models which forensics teams, police agencies, and analysts can use to build the profile of a criminal.

In March 2019, UTM Forensic Science student Charmaine Rodrigues published an article with instructor Eugene Liscio about how she and Liscio used a FARO Scan Arm to capture footwear impressions and analyze the impressions in CloudCompare.

“FARO has revolutionized all these areas in [terms of] what we can do,” says Eugene Liscio, an instructor at UTM and a 3D forensic analyst. The areas include documentation of forensic evidence, analysis of findings, and visualization of reports, areas that his company, AI2-3D, specializes in.

The FARO system is a device that’s widely used at AI2-3D. It’s a laser scanner which sweeps an area horizontally and vertically, capturing millions of data points which are later colour-coded.

“Laser scanning in general started in the late 1990’s,” explains Liscio. Since then, police have started using laser scanning and FARO to capture 3D renderings of crime scenes. FARO creates a point cloud—a set of data points in space that give an accurate depiction of the depth and space of objects.

Liscio says that “CloudCompare is interesting. It’s [also] free.” Created by French software engineer Daniel Girardeau-Montaut, CloudCompare is a software program that allows you to digitally compare point clouds.

FARO, CloudCompare, and point clouds have enabled many advancements in forensic science  and were the fundamental pre-requisites to the paper published by Rodrigues and Liscio.

“[The research] is a grueling process,” says Liscio. Liscio and Rodrigues worked closely under the FSC481Y: Internship in Forensic Science course which pairs UTM students with mentors. “I was a mentor for [Rodrigues], but she really put in the work. Like with all research projects, [our project] began with a review of literature. There were shortcomings along the way, ethical components, and variables.”

Using a FARO laser scanner, Liscio and Rodrigues demonstrated how a point cloud of a footwear impression can be constructed. The FARO Scan Arm converted the 2D footwear impression into 3D colour-coded evidence which was then analyzed through CloudCompare and compared with other footwear impressions. Through this process, agencies can draw conclusive data from footwear impressions.

Although Liscio admits that footwear impression evidence hasn’t been widely used traditionally, footwear impressions can play a role in identifying and ruling out suspects. Furthermore, with the advent of new technologies, the field is growing rapidly.

“In forensics, our next steps should be to continue to improve the analysis part of our findings. We have found new technologies that help in the documentation process. The real challenge is in the analysis,” says Liscio. He is currently focusing on infrared technology, identification, and bite mark analysis alongside working closely with his company, AI2-3D.