Straight guys have been claiming they just had to beat up gay guys as they were struck by 'gay panic' in court cases for years.

'Gay panic' is when a gay man comes onto you and you go temporarily insane and lash out, they've said. It has been successfully used in a number of cases to lower charges and sentences. Even the lawyer of Matthew Shepard's murderer Aaron McKinney tried to use it, but was struck down.

And now scientists have said it is all just made up.