That doesn't actually work outside of the movies. It takes a considerable amount of air in your system to actually do anything. Just connecting or changing an IV will introduce about as much air as the movies claim will kill you.
The autopsy would spot the needle wound, as it would have occurred prior to death, not having enough time to coagulate.
It would be best just to let them live. If they're a horrible person, that's a worse fate than death.
It would be best just to let them live. If they're a horrible person, that's a worse fate than death.