[Update: The man in question turned himself in.]
According to Yonhap (via the Segye Ilbo) yesterday a netizen posted a video of a middle aged man groping a woman asleep (or passed out?) next to him. It was taken at Sincheon station on Line 2 on the last train headed for Sindorim at 12:30am Tuesday night.
Perhaps in the future gropers might want to rein in their hands if people around them have their phones out.... which would probably put a stop to all groping on subways. Police are currently investigating the case using CCTV footage and traffic card ID records.