So this is a thought I had a bit back: is evidence obtained by a superhero admissible in court?
Superheroes have appeared in official proceedings in costumes, like when the Flash was on trial for murder or when Spiderman was in a Senate hearing (his testimony stricken from the record because of his mask, however). Often times, however, it's harder to see them in an official prosecution role because they are not officers of the law. Regardless of what any superhero does and whatever authority they may have, the vast majority are not officially part of any government organization that would allow them to act in the capacity of, say, a police officer.
Also, consider the fact that in most canon, Batman and many heroes are considered to be "dangerous vigilantes" and their actions are technically illegal. Batman is an excellent example. He does a lot of illegal things. Most of his evidence would be questionable because he would be constantly taking the fifth since most of his actions are incredibly illegal, such as dragging a man down the streets of Gotham with his face inches from the asphalt in order to get information. He is a private citizen and not bound by police rules, but at the same time his inherent vigilante nature does really cloud anything he could provide because of the questionable legality of how it was obtained.
It's a weird sort of thing, since yeah, cops do end up arresting Luthor and Doc Ock and then going into the dual process, but can Spiderman be called to the court as a witness? He seems like a hard guy to Subpeona, and wearing a mask to court is usually against the rules.
More later, this is something that demands research.