i wouldnt say anything. this is because its not my responsibility to tell my friend to do the right thing. any normal person knows right from wrong so if my friend decided that not confessing to the crime and letting someone else take the blame is the right thing to do, i cant do anything about it. if its a serious crime, there's always potential that my friend could get convicted many years later, and if that happens, so be it. they probably had it coming either way.