How does the mafia get away with murder?

[KidCharlemagne]

Beyond a few exceptions it seems that the mafia gets away with an undue share of murders. Witness intimidation notwithstanding, it seems pretty rare that the prosecutor can ever come up with any physical evidence. Now, I watch my share of those forensic science shows on the Discovery Channel and I find it hard to believe that anyone can get away with murder nowadays let alone a murder where law enforcement can probably pinpoint to a group of 5 the murderer in a mob killing. What do they do different than everyone else to avoid leaving physical evidence? Sure they get rid of the body but if you've ever seen "The New Detectives" that doesn't seem to be much of a hindrance these days.