Smoking Gun: Minkan Kasouken Chousain Nagareta Enishi

Nagareta Enishi is an eccentric, donut-loving forensic scientist at the private Chiyoda Forensic Science Laboratory. Nagareta mostly deals with civil issues and unsolved cases. His first few involve proving the truth behind an incident of public-transport groping and determining whether a 5-year-old case was a suicide or simply an accident. However, there's also a deadly mystery to be solved from Nagareta's own past... (Source: MangaHelpers)