It’s easier than you think to define knowledge. Here’s the Massachusetts Rules of Professional Conduct Definition.
(f) “Knowingly,” “known,” or “knows” denotes actual knowledge of the fact in question. A person’s knowledge may be inferred from circumstances.
All us epistemologists can sleep easy now. (As noted in previous post, I’m all of a sudden very interested in how “knows” is actually defined at law, but I don’t think this is going to help.)