Shunichi Ishihara, a senior lecturer at the Australian National University, recently gave a presentation on the infant science of chatroom forensics, now seen as a tool to use to catch pedophiles.
The way people chat online is fairly distinct. It isn't conclusive, but you can ramp up a high probability that you (or do not) have the right person. Law enforcement can compare incriminating texts or chatlogs with those known to belong to a suspect. Mind you, it isn't conclusive, but much of forensic science (handwriting, voice, etc.) is not.
If this is mysterious to you, Ishihara offers up examples from people unknowingly chatting with police officers - and points out the incriminating giveaways such as double question marks, ellipses, consistent capitalization of the first word, lack of punctuation and complete lack of capitalization.
Conclusive? No. But it can bolster a case - or suggest that the suspect is the wrong guy.
Fascinating read . . .