We haven’t had a case dealing with online troll yet !! However this case we found online is so relevant and sensible, we can not stop ourselves from linking it. It has abundant information on both legal and technical aspects of dealing with a troll. Most importantly it talks in detail about the psychological effects of trolls and how this could be devastating. Finally there is an interesting twist in the tail and it seems to be common occurrence in most of the cases we dealt with as well. Check the blog at http://www.traynorseye.com/2012/09/meeting-troll.html and also the technology feasibility of the same at https://evertb.wordpress.com/2012/09/26/tracking-a-troll/
Based on this blog Forbes came up with a article which details steps as well as information on both
1) taking law enforcement approach and
2 ) Figuring out yourselves approach. (DIY)
Step 2 is faster and less cumbersome provided you have some web suaveness. Sometime step 2 may not work if the criminal is savvy and has taken lot of precautions himself/herself. But as they say no one is truly anonymous in the internet.