Louis Theroux's LA Stories: Among the Sex Offenders, BBC2, TV review

Louis Theroux in his new documentary 'LA Stories' (BBC)

The main subject of Louis Theroux's LA Stories: Among the Sex Offenders on BBC2 last night was called Prentice (albeit with an "ice", not an "iss"). Craig Prentice ran a residential facility for sex offenders in California called Pathways.

He had a professional manner, a management-speak vocabulary and one of those mobile phone head-sets. He also had his own "offending history", the details of which were withheld until the end of the film, then delivered to devastating effect.

We know that not all sex offenders wear tinted glasses and carry sweeties in their pockets – of course they don't. But the variety in appearance, background and personality of Louis' interviewees still somehow came as a surprise.

There was Amy, a glamorous red-head who had been convicted of abusing an underage boy, and Randy, a shambling, likeably sincere flasher. When Louis suggested that his belief that women welcomed such behaviour might be self-delusion, Randy's response was most amiable: "Yeah, yeah... I can see what you're saying, it makes sense."

These odd interactions were motivated not by curiosity – or not only – but by the hope that a better understanding of sex offenders might lead to better public policy. Clearly, California's current laws – restricting areas of residence and listing parolees on a public database – are ineffective. As a consequence, sex offenders are often homeless, harder to monitor and much more dangerous.

Up in the Hollywood Hills, Louis found a former Pathways resident living in his van. Tattooed and handsome, he looked like the bad-boy love interest in a teen movie. He didn't want to talk about his offence and challenged Louis to a pull-ups contest instead. It was the kind of invite Weird Weekends Louis would have jumped at, but this late-period Louis is different. There's no bumbling Britishness, no kooky-for-kooky's sake, just that unerring ability to ask the most revealing question at the most provocative moment.