If I see a crime happening and jump in to protect the victim and end up killing the perpetrator, is that jail?

You can use deadly force to stop anothers use of unlawful deadly force. And you can use deadly force to protect another person.

Yes, you can shoot the person stabbing the woman. You can hit them in the head with a stick. You can do whatever it takes to protect that person.

It must be mentioned that all felonies in Texas will go before a grand jury. So it will be up to them and them alone if charges are presses. Not a judge, DA, cop, etc.....

http://www.statutes.legis.state.tx.us/Docs/CN/htm/...

So if you kill someone (justifiably or not) it will be presented to a grand jury. They will look at what you new at that time or what you should have reasonably known.

Just like Dirty Harry said:

Harry Callahan: Well, when an adult male is chasing a female with intent to commit rape, I shoot the bastard. That's my policy.

The Mayor: Intent? How did you establish that?

Harry Callahan: When a naked man is chasing a woman through an alley with a butcher's knife and a ****** (aroused), I figure he isn't out collecting for the Red Cross!

You are allowed to take reasonable action to defend somebody else from a crime. So yes, you could defend someone with force and not get in trouble.

The most important thing to remember, though, is that you can only take reasonable action, which is not the same as "kill anyone you want". If you use excessive force, you don't have the same legal protections and can still get in trouble. Killing someone in self-defence (or the defence of others) is only justifiable in extreme circumstances. And also, simply because you think your actions were reasonable, doesn't mean the police have to agree with you.

In any real situation, the police will investigate the matter, consider the evidence, and make their own decision on whether or not your actions were reasonable. If they don't think they were, you can be charged with a crime, be it manslaughter, murder, assault, or whatever- you then have to convince the judge your actions were reasonable.

Chances are you will walk because you had a reasonable belief that such action was needed to prevent the killing of another person.

depends who you are. every circumstance is different or if its public or on many other things but if it was reasonable amount of force and the only way to protect only you know and weather you go to jail or not it should be whats in your own conscious

probably manslaughter and walk. but who knows about the justice system now adays. its corrupt.