How is culpability determined in the following strange case?

Question

I'm a murder mystery writer and recently I came up with an interesting idea for a murder method, but I was curious in particular legal logic behind it.

Let's say two adults - Persons A and B - decided to shoot their BB guns at the other, for some reason. Unbeknownst to Person A, a third party hours prior - a Person C - replaced A's BB gun with an actual gun that looked exactly like the original BB gun. When Persons A and B shoot at each other, B of course dies.

Let's say later, in the course of the case, it was proven beyond a doubt that Person A didn't know he had an actual gun. On top of that, it was conclusively proven that Person C was the one who switched the BB gun with an actual gun. Would Person A still be convicted or face some sort of legal trouble? Additionally, would Person C ever be arrested, even though he technically wasn't the one who killed Person B?

Answer 1

It is a good idea for a story: that’s why it’s a trope

It features (with drugs instead of guns) as the core plot point of 2019’s Knives Out.

Shooting someone with a BB gun is problematic because it’s hard to see what legal justification there could be for that type of assault. However, if we instead thing of paint ball guns, C is a murderer and A & B have committed no crime.

Real life examples:

• While performing a suicide scene in a production of Mary Stuart by Friedrich Schiller in Vienna, actor Daniel Hoevels accidentally slit his own neck, as the theatre company's order for the originally sharp knife to be dulled for the stage was overlooked; a police investigation never determined who was responsible, or whether it was due to negligence or a deliberate attempt to kill or injure him. The wound was almost fatal, but Hoevels quickly returned to the stage after emergency treatment in the hospital.

• Never treat a blank in a gun as harmless. They can maim or kill you. Anyone who says otherwise is not your friend. Read the article here on Gun Safety for more details.

  • There have even been two sad cases listed in Fatal Method Acting: Brandon Lee, accidentally killed during The Crow because the crew left a cartridge in the barrel before loading the blanks, which then hit his spine; and actor Jon-Erik Hexum, who in-between takes of the show Cover-Up, goofed around with a gun and by firing it into the side of his head, had a blank cause enough trauma to shatter a quarter-sized piece of his skull and propel the pieces into his brain.

• More than 20 illusionists have been killed performing the 'bullet catch' trick. It is generally considered the most dangerous magic trick as so many things can go wrong. Some of those killed were murdered when someone (often their partner/assistant) substituted a live round for the blank or—in earlier days, when single-shot black powder guns were used—placed the ball back in the barrel after it had been removed.