They weren't trying to imprison him, they were trying to gather evidence of who murdered Jane, which would result in imprisoning that person. Jane's killer was

They weren't trying to imprison him, they were trying to gather evidence of who murdered Jane, which would result in imprisoning that person. Jane's killer was in a strange circumstance. So was Jane, what with being murdered and all. The unconventional means of getting a confession were not immoral or unethical at all, IMO, and the courts certainly agreed they were admissible.