>...and even for felonies the arresting person must reasonably believe that the arrested party committed the felony, but the felony must also have actually occurred, otherwise the arresting person is liable for false arrest even with reasonable belief that the arrested party had committed a felony.

I don't believe this is true, though I suspect we're getting off into the details that vary from state to state. Certainly you're asking for trouble making a citizen's arrest unless you're pretty damn sure you know exactly what's going on.