User blog comment:Anarchic Operations/Getting Away With Murder/@comment-28266772-20160619173849

I could write forever on this, but you might be interested in Harold Shipman. He accrued the highest kill count of any serial killer in the UK - an inquiry found he was responsible for at least 218 murders, though he was only charged for definite on 15. He was an 'angel of death' - I think that's what they're called. But basically, healthcare professionals who take advantage of their positions to become serial killers. They often accrue seriously high death tolls because of this strange synergy between caring for vulnerable people, and needing to kill without getting noticed. And Shipman was only caught because a local taxi driver noticed a puzzling pattern with the old women he would drive to the doctor's every week.

So I guess yeah - corpse disposal is the big one. I think the perfect murder takes place in the exact place you expect to find a corpse, and involves someone who's death wouldn't be questioned. It also helps if the killer is the guy who determines whether cause of death is natural or not.