Which Was the Murderer?

Robert Barr was a Scottish- Canadian short story writer and novelist. Robert BarrТs principal talent lay in the cleverness and ingenuity of his plots, particularly in his ability to devise ironic twists to otherwise straightforward situations. Mrs. Forder is a loyal wife, who loves her husband dearly. This morning is typical for her. She attends her morning duties as usual, while her husband is working in the garden. She has no premonition of evil, that trouble can happen. Suddenly she hears the click of the front gate and immediately hastens to the door. Outside she sees just two things- first, her husband lying on the grass senseless,and second, a man trying to undo the fastening of the front gate with a smoking pistol in his hand... Who is this man with a smoking pistol in his hand? And will the judge bring him a verdict of guilty?