If you actually have information and there's not even the slightest possibility that it could turn bad for you, then sure, be a good citizen. But if you don't

If you actually have information and there's not even the slightest possibility that it could turn bad for you, then sure, be a good citizen. But if you don't have any information, or if there's even the most remote possibility at all that you could somehow be implicated by the information you have (or by the fact that you have the information in the first place), then plainly, simply, and politely: "I have nothing to say" and "May I go now?".