The US has operated ‘Megan’s Law’ since 1994, following the rape and murder of seven-year-old Megan Kanka in New Jersey by a sex offender living in her neighbourhood.
Each state handles sex offender registration and community notification, but must decide on what information is made available and how it is distributed.
The Murphy case has led to calls for a similar system to be instated here, but some experts have said the system can be prone to vigilantism, while occasionally innocent people can come under attack in cases of mistaken identity.
Kieran McGrath of the National Organisation for the Treatment of Abusers (NOTA) Ireland said politically the idea of a Megan’s Law is very popular and “extremely cheap”, but it can be “used as a substitute for real supervision and real monitoring places responsibility on community to protect itself”.
“Sex offenders aren’t stupid – they are much less likely to offend next door and more likely to go to next parish where they don’t know anybody,” he said.
Research in Britain on the effectiveness of Megan’s Law has also found no subsequent reduction in second-time offences and, just 80% of offenders registered upon release from prison, compared with a 97% of registration in Britain.
There, where there has been a campaign for an equivalent to Megan’s Law, a number of cases of mistaken identity have taken place:
* Paul Cooper, 40, was beaten to death by a gang of men at his flat in Heywood, Greater Manchester in March 2005.
* In 2000 Michael Horgan, a 55-year-old father of two from south London, was targeted by an anti-paedophile group after a newspaper published his name, which he shares with a paedophile who lives in the area. Police had to place a permanent guard on his house.
* In 2000 the Portsmouth riots saw four innocent families forced out of their homes by mobs campaigning to rid their community of paedophiles. Police had to plead for calm after revealing the four families had no history of child abuse.
* John Brown, a 79-year-old living in Belfast’s New Lodge area, was held down and kicked before being shot in both knees after the IRA wrongly believed he was a paedophile. Another man in a loyalist area was attacked by paramilitaries in July 2000 after it was wrongly asserted a sex offender was living in his house.
* A female registrar was harassed in her South Wales home because neighbours confused “paediatrician” (on a nameplate beside her door) with “paedophile”.
* In recent years a man mistaken for Jon Venables, one of the killers of toddler Jamie Bulger, had been forced with his family to move several times.