Murder by Television is a 1935 mystery film starring Bela Lugosi, June Collyar and Huntley Gordon. Also known as The Houghland Murder Case (USA)
James Houghland, inventor of a new method by which television signals can be instantaneously sent anywhere in the world, refuses to sell the process to television companies, who then send agents to acquire the invention any way they can. On the night of his initial broadcast Houghland is mysteriously murdered in the middle of his demonstration and it falls to Police Chief Nelson to determine who the murderer is from the many suspects present.

Kev,
Nice twist for the ending
Rich