Human hair is a classic piece of crime scene evidence. But proving whom the hair belongs to can be, well, a bit hairy. Traditionally, an expert visually compares hairs under a microscope, although this method lacks quantitative validation. Researchers at Lawrence Livermore National Laboratory are aiming to change that. The human hair shaft contains more than 300 different proteins, which gave the scientists an idea to create a system for turning hair samples into molecular fingerprints by examining single amino acid variations between individuals. “It is a method that goes beyond the ambiguities of appearance,” says team member Deon S. Anex. By using mass spectrometry to study hair proteins from 66 European-American subjects, Anex and his colleagues show that “hairprints” have only a one-in-12,500 chance of being shared by two individuals, making it a good method to rule out the innocent in criminal investigations (PLOS One 2016, DOI: 10.1371/journal.pone.0160653). The approach originated with study coauthor Glendon J. Parker, who holds a patent for conducting genetic analysis on human hair and is the founder and CEO of Protein-Based Identification Technologies, a company aiming to commercialize the technique.