The wear patterns of your jeans aren’t good forensic evidence

Enlarge / The "barcode" pattern of light and dark points along the seam of a pair of jeans. (credit: -Bine- / Flickr)

Is every pair of jeans like no other? According to the testimony of FBI forensic analysts, the patterns seen on denim are reliably unique and can be used to identify a suspect in surveillance footage.

The problem is, this technique has never been subjected to thorough scrutiny, and evidence acquired through it may not be as strong as it has been claimed to be. A paper published in PNAS this week puts denim-pattern analysis through its paces, finding that it isn’t particularly good at matching up identical pairs of jeans—and may create a number of “false alarm” errors to boot.

Shoddy evidence

For some time, there have been rumblings about the reliability and quality of commonly-used forensic techniques. In 2009, the National Academy of Sciences published a weighty report observing that, apart from nuclear DNA analysis, “no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.”