A DNA-matching technique used in forensics since the mid-1990s is now in question, according to new research. DNA found in cell structures called mitochondria varies greatly between samples from different tissues from the same individual, researchers found, meaning that forensic units may be mistaken when they exclude suspects because a mitochondrial sample from hair, for example, doesn't match mitochondrial DNA in their blood.
Mitochondrial DNA is often used for analysis because so many of the structures exist in cells that the genome can be read even in old, degraded samples. "I wouldn’t say that it throws other results out the window, but it does throw a curve ball," the study's co-author, a geneticist at John Hopkins University, tells Wired. He says forensic specialists seeking to compare DNA samples should ensure they use samples of the same tissue.