We find it hard to believe people would confess to a crime they didn't commit. But they do.

What can psychologists tell us about Mr Big?

Leading experts in false confessions argue that we (and therefore jury members) find it difficult to believe that someone could confess to a crime they didn't commit, difficult to tell when someone is lying, and difficult to accept that it's people's predicaments that drive their behaviour, not their character.

All this makes David's lawyers nervous about the trial. They try put up expert evidence so the jury can understand these things, but the judges threw it out.They said juries should be able to understand all that on their own.

But can they?

Could you?

Go to this episode on rnz.co.nz for more details