Know and protect your online reputation
There are lots of commercial applications for "knowing and protecting your online reputation." Just Google that last phrase. I'm not recommending any of them but they sure establish there's a demand.
There's also some free training developed by the Department of Defense (DOD). You can link to it below. If you don't check it out, at least give it to the person responsible for your agency's social media policy. If your agency doesn't have such a person, give your supervisor this article and suggest she read it "if there's any chance any of our officers might ever testify in a criminal or civil case."
The best defense against the defense is to go on the offense. Take the Officer Facebook Juror Credibility Test - each and every posting.