One blue eye and one brown

I know a guy who has one blue eye and one brown. I know this can be caused by injury, but this guy says he was born with it. Why does this happen?

its called heterochromia and it can be caused by injury, disease, or genetically inherited.

genetics..

its a mistake in the DNA that causes this, kinda like Albinos.

it certainly does happen
theres even a celebrity with blue euyes and one of them is almost all brown
also one on my friends had a blure eye and a green eye
its not common but there are people with two different coloured eyes
and yes, genetics is the cause
but I've never known anyone who had it from an injury
unless your talking about someone having to get a new retna
(from a donor) so they can see

I would think that its a mutation or somen like that...

I was told in Biology that it can result from an alteration to one of the genes controlling eye colour. It can be inherited, through injury or medical syndromes.