Police have been told they do not need to investigate rape cases deeply. But there is a better way

There is a somewhat distasteful expression that prosecuting barristers occasionally use after a jury has convicted. “I potted him,” they will say to anyone who happens to be listening, usually with a faintly repellent smugness.

There is more to prosecuting than “potting” a defendant as though he were a celluloid ball, important public service though that can often be. Prosecutors also have a critical role in protecting the innocent. A good prosecutor should never take an unfair point, and should never try to adduce clearly inadmissible evidence.

Above all, they should always disclose evidence that undermines their own case or supports that of the defence. The police too are under a duty to follow all reasonable lines of inquiry, and to reveal what they discover to the prosecutor even if it undermines a case they thought they were building against a guilty man.

Yet in recent weeks we have seen multiple highly publicised cases collapsing because of a failure to investigate important lines of inquiry at all – and a failure to disclose “undermining” evidence discovered when such investigations have been carried. Most of these have been rape cases in which vital evidence from phones and social media was either not properly investigated or not properly disclosed to the defence until practically the start, or even after the start of the trial.