This month, a judge in California cleared thousands of criminal records with one stroke of his pen. He did it thanks to a ground-breaking new algorithm that reduces a process that took months to mere minutes. The programmers behind it say: we’re just getting started solving America’s urgent problems.Piero Salazar is sitting at a wooden table, swamped by paperwork. His anxious family looks on.He’s one of around 50 or so people who have come to this community centre in San Fernando, near Los Angeles, to take part in an “expungement clinic” – a free service for those looking to get their criminal records removed or reduced. A team of lawyers, working pro bono, sit behind a long counter and call people forward when their number is up.