What do I do about someone blackmailing me in response to a civil suit?

I've filed suit against someone for tortious interference and in return, I'm affraid they're going to retaliate by trying to file a police report about something (they're loosely trying to allege witness tampering) that purportedly happened a year ago and that's supported with evidence that's shown to be forged. They've already tried to bring these allegations up to another party that briefly entertained them until they were presented with the unaltered documents. Would a reasonable DA even entertain this crap?