The issue focused by lawyers who argued at the High Court was whether officers used excessive force during the riot at Glasgow Central Library on 21 December 1989.Lawyers representing staff said police officers used excessive force during the disturbances at the library on 21 December 1989.Three officers were cleared of wrongdoing over the riots but former detective sergeant Stuart Knox was cleared of manslaughter by gross negligence and misconduct in public office.Three officers were acquitted of manslaughter by gross negligence and misconduct in public office and PC Duncan McNamara was acquitted of manslaughter by gross