“Brain fingerprinting,” a controversial technique using involuntary brainwaves that could reveal guilt or innocence is about to take center stage in a last-chance court appeal against a death-row conviction.

The accuracy of this technology lies in its ability to pick up the electrical signal, known as a p300 wave, before the suspect has time to affect the output. “Brain fingerprinting doesn’t have anything to do with the emotions, whether a person is sweating or not; it simply detects scientifically if that information is stored in the brain,” said inventor Dr. Larry Farwell.