Grand Theft Auto 5 is trying something new by featuring three lead protagonists, each with their own specialized abilities. But what's to stop you from finding one of your alter-egos and murdering him in cold blood, other than a general sense of right and wrong? According to Rockstar, quite a bit.
Responding to a series of fan questions, Rockstar said that each of the characters are meant to be living out their own lives, so popping into one might put you in the middle of a family scuffle with Michael, or find Franklin flirting. Their locations won't always be plainly obvious, and Rockstar says it's "not always easy" to track them down. If you do find one of your fellow heroes, you can hang out with them, and even smack them around, but you can't kill them.
"They all have remarkable powers of recovery and good health insurance," the blog states. "The game is based on playing all sides of these three characters' interwoven stories rather than having generic, interchangeable leads, so permanently killing a major character in that way wouldn't make sense. If a player is determined enough though, they may well find a way to badly injure one of the characters and switching to that character would just put you in the hospital to continue where you left off."
So basically, it sounds like each of the characters become Wolverine when you're not in direct control of them. Disappointing as it may be to budding psychopaths, that move does maintain Rockstar's ability to tell a story without completely breaking it.