Death Row inmate pins freedom hopes on novel brain test

A convicted murderer facing a death sentence in America hopes that a new forensic science technique called "brain fingerprinting" which tracks human memories will rescue him from the executioner.

Jimmy Ray Slaughter was convicted in Oklahoma of the 1991 murders of his ex-girlfriend and their baby daughter, and sentenced to die by lethal injection. He always said he was innocent but his appeals procedure against the death sentence was running out when his lawyer heard about the technique. The tests showed that Slaughter did not commit the murders and an appeals court is expected to make a decision soon on whether to set him free.

Brain fingerprinting is supposed to assess the truthfulness of what a suspected criminal is saying by monitoring electrical "flashes" in the part of the brain associated with memory. The suspect is given or shown words, images or objects of the crime scene or a weapon that only the police or the person who committed the crime would know about. An involuntary electrical signal in the brain - known as a P300 wave - registers recognition. It happens so fast, within 300 milliseconds, that it is deemed impossible to fake a response.

The technique has already been accepted as valid by courts in some US states and is being considered for use by the FBI and CIA which have been impressed by tests.

Its inventor, Dr Lawrence Farwell, a neuroscientist from Seattle, explained: "We were able to tell with a 100 per cent accuracy who was an FBI agent and who was not by flashing details on a screen that only agents would know and measuring their brain responses to see if they recognised those or not."

The conventional lie detector test, the Polygraph, invented in 1921, has never been accepted by courts. It monitors signs of anxiety like sweat, pulse rate and blood pressure but it has been shown that some people can fake reactions to fool it.

Dr Farwell said his technique does not depend on subjective factors. "It has nothing to do with whether a person is anxious or not and, in fact, with whether they are lying or not. It simply detects in a scientific, objective manner whether certain information is stored in a person's brain." Dr Farwell said his apparatus has already been used to clear one convicted murderer. The method has also led to the conviction of a murder suspect, JB Grinder.

Dr Farwell said: "Brain fingerprinting showed that the record in his brain matched the crime scene, he knew the salient details about the crime." Grinder confessed to that murder and those of three other young women and is now serving a life sentence.