I’m not a Rothbardian on law though my views mostly coincide on any practical point - you can read my position in detail here.
First of all, there will always be crimes which go unpunished even if you designed a social order whose sole goal was to ensure that no crime goes unpunished (Oh wait, that’s America circa 2012).
Second, standing is a matter of precedence (in my view, even if this is contra Rothbard) - that is, no one has a right to sue if the victim or the victim’s family chooses not to sue. They have right of refusal. By not suing, they are essentially rendering null any other claims on the aggressor. The argument is simple: “Bob is suing me for damages, claiming that I hurt Alice. Yet Alice is not even a witness for Bob on this account, let alone has she sued me herself. If anyone were to sue me for hurting Alice, it would be Alice herself. Since Alice is not suing me, clearly I have not harmed Alice in any way that concerns law.” Case closed.
If no one is there to claim precedence (a victim or victim’s family), then there is nothing preventing a lawsuit by any interested party. For example, let’s say there is a charity called Homeless Angels that investigates murders of homeless people and brings their perpetrators to law. The defendant cannot dismiss the suit pro forma along the above line of argument because it simply does not apply - the victim is dead and, by virtue of the fact that he is homeless, there is probably no family who could sue on his behalf. In this case, why shouldn’t any interested party be able to investigate and file suit on the matter? The monetary award (if any) should go to the party that took an interest in the matter since - by taking action - they have homesteaded it.
The essential question is who initiated the aggression. This is the origin of the Hollywood mythos of the Western gunslinger throwing a gun at the feet of his intended victim and challenging him to “pick it up.” The idea is that the gunslinger is trying to paper over his intended murder by being able to call a witness to testify that the now dead man “went for his gun first”.
In most cases, this is a fairly simple problem to solve using witness testimony, etc. However, the nitty-gritty details of the corner cases can become complex and may not be solvable by law in sufficiently gray areas.
The term you’re looking for is preponderance of evidence. It’s a really horrible principle because it implies that evidence is like some kind of massive substance which can be weighed on two sides of a scale. Of course, this idea only makes sense in a statist monopoly court where “the Judge” sits on a judgment throne like God Himself and “weighs the souls” of the parties. In private law society, the arbitrator is just a contractor, someone hired to assist the disputants in settling their dispute. The impetus for settlement comes from the disputants themselves, not from “the Judge.” The sole criterion of reasonableness or evidentiary finality is the assent of the parties themselves to a settlement.
This still goes back to the Judge-on-the-Throne-Weighing-Souls theory of law.
Clayton -