A troll is likely to end up in situations where he has made some really wild claims about something. When facts and proof is posted, the troll needs to ignore or evade that in order to keep up appearances. This is usually done by snipping it out of a followup and then claim something hasn't been proven, or replying to proof and using diversion or ad hominem's to divert attention away from the proof.
Another common tactic is to cut and paste his first claim again, in spite of it being questioned and/or proven incorrect