Hi. Had read coutless times in congress `noob murdered for fun' stuff. No one brings the murderer to justice, cause like world is too big, rangers are unmotivated (what reward noob can offer?), nobody cares and so on. So here is the idea.
Basic scheme: post death voting scheme. After death by pvp killed player can cast a vote against it's murderer. Every time the vote is cast a game of chance is played, outcome of which is either death or not. For this game a variety of functions can be used. For example: 1/2^(N), where N is the number of killed people by the player against whom the voted is cast. So, in this example, the probability to survive 5th murder is like 3%.
This particular scheme is a subject to tuning - e.g. choosing a function, a parameters, may be introducing decay of votes and so on.
Advanced: the same, but with some modifications against growing murder alts. The same stuff, but killed guy can choose against who he casts a vote. He can choose among a group of people, which are related to killer. Relationship is measured in consumed items (curios, food). Every item has a creator, so before voting, we can form a group of people, where each involved will have a number denoting his participation in `raising' the murderer. Thus, smart victims can try to target most valuable account.