Studies suggest most of us can detect lies at a rate only slightly better than chance. So what if technology can give us a more accurate reading? The polygraph has been used as a lie detector since the early 1920s, but in most jurisdictions its results are not admissible as evidence in courts. Recent developments in neuroscience, however, suggest brain scanning may provide a more accurate and more direct window into truthfulness or deception. But would and should we want to use such technology, and if so under what circumstances?

In 2010 Dr Tom Ziessen was awarded a Winston Churchill Travelling Fellowship to investigate and make a film about how brain scanning technology is currently being used to attempt to detect truth or lies in India and the USA. In India, thousands of people have been scanned using an EEG-based system (monitoring the electrical activity of the brain), developed by clinical psychologist Dr CR Mukundan, who claims his system can detect experiential knowledge, for example testing whether a suspect took part in a crime. This evidence has already been presented in Indian courts and there have been convictions based, at least in part, on this evidence. In the USA, two companies offer fMRI-based lie detection services (functional magnetic resonance imaging). Neither has yet provided evidence that has been accepted in courts, but it has been considered in pre-trial hearings by judges in at least two cases. Is it just a matter of time before it is allowed? If so what impact will this have on the legal system and will we soon see attempts to introduce lie detection in UK courts?

Ziessen’s short film explores the arguments for and against the use of brain scanning based lie detection through interviews with scientists, lawyers, ethicists and those offering commercial lie detection services.