In the movie Harry Potter and the Deathly Hallows Part 2, Harry makes use of the Imperius curse on a Goblin to get them into Gringots. I'm fairly certain in the books that the fate of this Goblin is never addressed, but in the movies, he is humorously incinerated by the dragon trapped inside. This would make them murderers wouldn't it?
Harry's use of the Imperious Curse did appear to addle the Goblin's brain enough that he was killed due to Harry not ordering him out of the way, so maybe if you really stretch it you could make a case for involuntary manslaughter in the real world.
As it is though, this is the magical world and Goblins aren't human beings, thus it wasn't illegal for Harry to use an unforgivable on him under wizarding law:
"Now. . . those three curses - Avada Kedavra, Imperius, and Cruciatus - are known as the Unforgivable Curses. The use of any one of them on a fellow human being is enough to earn a life sentence in Azkaban."
-"Alastor Moody" in Harry Potter and the Goblet of Fire
Furthermore, Harry didn't order the goblin to do anything, so he should have just waited outside the door when it locked behind them, the fact that he wandered over to the dragon would indicate he was starting to regain control over his actions.
Even if the Goblins somehow blamed Harry for it (and they probably didn't know seeing as Voldemort killed all of the ones involved shortly afterwards), there's no way the Ministry for Magic would prosecute him over it after he just saved all their lives.