You're in the pub and trouble starts. There is shouting, someone is stabbed, they die. It happened right in front of your eyes and the police want to speak to you. But what exactly did you see?
It's long been accepted that eyewitness testimony may not always be as reliable as it seems. The problem is people simply don't remember exactly what happened, say psychologists

On one day the participants went for lunch in a local pub, which was really filled with actors, stuntmen and 10 hidden cameras. A fight broke out and someone appeared to be stabbed and killed. The whole scenario unfolded over 20 minutes.

During the drama the eye trackers - still being worn by some volunteers during the mock robbery - were able to pinpoint exactly what people were looking at and compared to what they reported. The differences, say those involved, were in some cases staggering.