A Somali man went on trial over the killing of three people and injuring of several others in a stabbing attack in southern Germany last June in proceedings to determine whether he should be held in a closed psychiatric facility. Investigators believe the man was mentally ill at the time of the attack in the city of Wuerzburg, and so the trial will therefore establish whether he can be held criminally culpable He has been charged with murder, attempted murder and serious assault. His defence attorney, Hans-Jochen Schrepfer, said the suspect had been suffering from a psychotic episode and "voices…