UBC study finds courts overestimating reliability of forensic evidence like ballistics and bloodstain analysis

Evidence courts depend on in criminal trials may not be as reliable as decades of courtroom use have suggested, according to new research from the University of British Columbia that calls for stricter standards and better scientific literacy among legal professionals.

Sara Gordon, an associate professor at UBC's Peter A. Allard School of Law, led the study examining three key forensic techniques: ballistics evidence, bloodstain pattern analysis, and police dog alerts. Her findings reveal significant gaps between what courts assume about these methods and what the science actually supports.

In ballistics testing, investigators misidentified bullets 37 per cent of the time. For bloodstain pattern analysis—a technique Canadian courts treat as solid proof—the picture was mixed: analysts correctly classified patterns 70 per cent of the time on solid surfaces but only 62 per cent of the time on fabrics. The practitioners often rely on concepts like fluid dynamics without formal physics training.

Police dog alerts fared worse. A study from Australia found nearly 75 per cent of police dog alerts were unfounded, prompting researchers to call for clearer standards for sniffer dog training, certification, and performance monitoring.

"Just because a technique has been used in court for decades doesn't mean we should take its reliability for granted, especially when someone's liberty is at stake in a criminal trial," Gordon said. "There haven't been many rigorous scientific studies, and the studies that are now emerging suggest that many of the conclusions police officers have testified to in court are not supported by the science."

The research calls on judges to ensure expert evidence is backed by science and urges greater scientific literacy among lawyers and judges. Gordon hopes the work will help courts better understand the limitations of forensic techniques and present evidence in ways that accurately reflect what the science can and cannot tell us.