Being able to detect if a person's lying is a pretty nifty trick. But traditional polygraphs are no longer reliable because liars have learnt to fool these machines. Instead, scientists are developing the next generation of lie detectors that tap straight into our brains. Using brain-scanning technology they are beginning to probe our minds and tell if we're lying.
The tests could help the wrongly accused prove their innocence and help police to find the guilty. But does this take Big-Brother-style surveillance a step too far?