If it was a 'clean' hit, why would there be record of a homicide? From what I've read, it sounds like a clean hit could/would be made to look like an accident.
The US gov produced a document a while back about assassinating people - though for the life of my I can't find my copy so it's possible there wasn't anything novel enough in there to be worth keeping it. I believe they recommended causing someone to fall from a high place. I'd imagine by grasping their ankles and then tipping them over the edge; though the precise methodology for the tripping was redacted in the version I saw.
