FEW parole-board decisions have been as closely scrutinised as the proposed release of John Worboys in January. The announcement sparked fury. MPs demanded an explanation. David Gauke, the justice secretary, considered an unprecedented legal challenge but settled for a review of the whole system of how prisoners are released.

On February 7th a high-court judge duly allowed a judicial review of the decision, at the request of two victims. In 2009 Mr Worboys, a taxi driver, was jailed for sexually assaulting 12 women. He is believed to have attacked about 90 more. It is unclear whether he will be freed, but the case may lead to a reform of the parole system.

One of the main concerns of Mr Gauke’s inquiry, to be conducted by the House of Commons justice select committee, is transparency. The parole board acts like a court, deciding whether to release convicts, many of them on life or open-ended sentences. The rulings are based on testimonies from experts, like psychotherapists. Many involve oral hearings held by parole-board members. Public safety is paramount—and their record is impressive. In 2016, 3,800 convicts were freed, but those released committed only 22 serious offences.

However, the thinking behind the board’s decisions is not made public. That leaves victims in the dark and undermines public confidence in the system, as Mr Worboys’s case shows. The victims seeking to block his release do not know the parole board’s reasons. Many, including Nick Hardwick, the parole-board chair, advocate a more open system. In Canada anyone can attend a hearing; in New Zealand the gist of decisions is published.

Yet too much transparency poses problems of its own. More media attention on prisoners’ cases may force victims to relive past horrors. Parole-board decisions are about assessing the risk of reoffending, says Laura Janes of the Howard League, a penal-reform charity. The judgments can seem counter-intuitive. For instance, research shows that remorse is not an accurate indicator of whether a prisoner will reoffend.

Convicts may also be reluctant to talk openly at hearings. And, once released, their safety may be harder to ensure. As Mr Hardwick told the justice select committee this week, reforms ought to be radical but carefully thought through.