You really think the main reason people aren't grudge killing each other because they are afraid of getting caught ? Look at the murder case % that goes unresolved even in the US - IIRC it was ~40% ? If you wanted to kill someone and were smart about it's probably not that hard to do - unless it's your spouse or something similar that makes you an obvious suspect - in which case it will also look suspicious to anyone investigating if you killed your wife because she was a drug dealer.