Ron Bigby is a poker player and Wall Street type who rubs shoulders with the criminal element in "Deep in Death". Bigby met John Allen whilst in a dive where he was gambling, and tried to help the other man out when Allen ran into financial trouble. His 'assistance' came in the form of an introduction to a drug gang looking for a mule, and the eventual outcoe was not only Allen's death, but also the theft of his corpse from the coroner's van. When Beckett and Castle interview him, he starts out trying to impress, but when he grasps the seriousness of the situation, he's quick to give up his contacts. Bigby himself never seems like a serious candidate for murderer, and although he may face some kind of charges, presumably his cooperation with the police will be taken into account.