A Thunder Bay police officer is being charged by the Special Investigations Unit. In May, the OPP brought a man into Thunder Bay Police custody where the SIU says Constable Andrew Johnstone used subsequent force with him. Johnstone is facing one charge of Assault and will be in Ontario Court of Justice on August 20th. .Meanwhile, Thunder Bay Police say Johnstone is on desk duty and isn't suspended. He's been with the Police force for 9 years.