I've given numerous examples as have others on several occasions.
Each time you won't admit it.
The interesting thing about those few internet trolls who are brought before the courts is that ~ in common with the jailed troll mentioned by Lyall ~
http://www.guardian-series.co.uk/news/national/11198615.print/ ~ there seems to be a pattern that they are offenders known to the police or social services - drug abuse - mental health issues - interrupted education - attention seekers living insular lives.
For example, from the Guardian article - "Riley regarded Twitter as a chance to engage in "social banter" " ... and "he remained incredulous following a backlash from other Twitter users".
Which tells me the expectation this man had of social media was that - anything goes - and if he had discovered the joys of McCann bashing and stuck to that in his incredulity he wouldn't have been quoted as saying - " "Of all the sick things I've tweeted, starvation, genocide, rape and torture, it's the teacher from Leeds that outrages everyone the most." "
For the simple reason that as far as McCann bashing goes it seems the trolls have been given free rein and any successful prosecutions involving the McCann name relate to Madeleine being mentioned in conjunction with other missing or murdered children ... it appears there is carte blanche to malign her parents with the foulest accusations.
It should be noted that, Riley, the person jailed was prosecuted 'following a complaint to the police' no reference is made to who the complainant is.