You should never be a witness against yourself:  but there are many cases in which people incriminated themselves.

According to this talk, if you are living in the U.S.,  thanks to the Bills of Rights – you are protected! : one caveat – never ever talk to the police – whatever you say, I mean WHATEVER, you say, can be somehow and in some way to be used against you, at least according to this law professor:

Sincerely yours,