When the detectives go to the physics lab to gather information on Weiss, his desk drawer is locked. When the police move to force it open, another lab employee steps in with a key and opens it. Later, Weiss is confronted with what was found in the drawer as proof that he is guilty of murder. Although it might seem that the lab employee's ability to access the drawer would nullify its contents being tied specifically to Weiss, presumably the police later verified that the other worker lacked opportunity and/or motive, ruling out a potential defense for Weiss.