Law enforcement has done criminal profiling for decades and recognizes it as an invaluable tool.

CNN: Screening must include religion, ethnicity

Criminologist Prof David Wilson of Birmingham City University, who once worked on the sex offender treatment programme at Grendon prison, says psychological profiling can indicate whether such a criminal is less likely to re-offend - but ultimately, the nature of the offence makes it impossible to be absolutely certain.

BBC: Who, what, why: When is a sex offender not a risk?