Operation Valkyrie
Howson presided over German prisoner of war trials in Medicine Hat including the infamous case where POW Karl Lehman a suspected sympathizer with Operation Valkyrie was beaten and hanged by four fellow POWs on September 10, 1944. Bruno Perzonowsky, Walter Wolf, Heinrich Busch and Willi Mueller were hanged in Lethbridge, Alberta along with convicted murder Donald Sherman Staley on July 24, 1946 in what would be the largest mass hanging since the Northwest Rebellion.