Murdoch uses an ultraviolet lamp to detect drops of blood. The ultraviolet lamp, more commonly known as a black light, was invented by William H. Byler in 1935, some 30 years after the time of this episode. However as in many other cases where he invents something earlier but takes no credit, Murdoch invents what he calls "chemi-phosphorus luminescence" during the events of Murdoch Night in Canada (2012) to detect blood on a hockey stick. This is the tool being used here.