Where I come from, to sell out your friends is to sell your soul to the devil.
Grassing on a friend would be the quickest way to end up completely friendless and the quickest way to the local infirmary.

However, there are exceptions, murder being one of them and even that would depend on who was murdered and why.

Good friends are hard to come by. If you have one, keep them close and they're there for life, through thick and thin.

Like everyone else has said, it depends on the situation or the extent of how badly the compadres have offended. I'd sell them out if they didn't deserve saving. But if it's something minor like a bit of pocket theft, you know, the serious but slightly trivial stuff, then sure I'd protect my mates.

Depends how much your mates mean to you as a pose to how much you're willing to suffer.

^ definitely agree with that....

A misdemeanor wouldn't do anything.

Yeah I agree with that.
Although I'm not good at these questions. I can't really decide what I'd do unless I'm put in the situation. Even though I'd like to think I wouldn't sell-out.