Final answer:
A client cannot legally authorize a private investigator to engage in theft, as this would be a criminal act for both the PI and the client.
Step-by-step explanation:
No, a client cannot authorize a private investigator (PI) to take part in the theft. Private investigators must work within the bounds of the law, and theft is a criminal act, regardless of the client's wishes or perceived necessity. PIs are expected to conduct their investigations legally and ethically, and taking part in theft would compromise their legal standing and potentially result in criminal charges for both the PI and the client.