Think of it as a miniature light sabre. Scientists have unveiled a ‘plasma pencil’, a handheld device that generates a thin plume of charged gas that can kill bacteria, and could one day etch away tumours without damaging surrounding tissue.

Prosecutors in the United States say jurors schooled in crime investigations through watching TV dramas are making it tough to prove cases because they expect to see sophisticated forensic evidence, even in white-collar trials.