There's a wide gulf between concrete knowledge and belief.
I see an ambulance going lights-and-sirens behind me. I don't know they're on their way to or from a hospital, but I pull over because I have reason to believe they are.
Weird analogy. An ambulance has a very narrow scope of responsibility. Legal processes have a very wide scope. Clearly this is related to a legal matter and not an immediate medical matter. But the nature of the legal matter could be a very wide variety of things, ranging from lower court civil proceedings up to treason, etc.
I see an ambulance going lights-and-sirens behind me. I don't know they're on their way to or from a hospital, but I pull over because I have reason to believe they are.