British scientists have discovered a new way to tell twins apart using the melting points of their DNA. If both twins are suspects in a criminal case or identical twins are blaming each other for a crime, this can be an effective tool for investigators.

To find the subtle differences in twin DNA, researchers swabbed the cheeks of five sets of twins. The DNA was heated and researchers noted at what temperature the hydrogen bonds in the DNA broke. That is the "melting point." Each twin's DNA melts at a different temperature, usually resulting from lifestyle differences like sunlight exposure or smoking.

Previously, genetic mutations were used as markers for differentiating between twins, but lead researcher Graham Williams, according to a press release from the University of Hudderfield: "If such a mutation is identified at a particular location in the twin, then that same particular mutation can be specifically searched for in the crime scene sample. However, this is very expensive and time-consuming and is unlikely to be paid for by cash-strapped police forces."

The study, "Differentiating between monozygotic twins through DNA methylation-specific high-resolution melt curve analysis," was published in the journal Analytical Biochemistry.