Congrats to everyone who answered the previous question about counselors' duty to warn!
Duty to warn is also known as the Tarasoff Rule, and it originates from the landmark case,Tarasoff v. Regents of the University of California. This case set a precedent that requires therapists to warn anyone their client intends to harm. While it was a California-specific ruling, it's generally spread to become a professional mandate.
The implications of this get complex, though. For instance, some states require therapists to warn their clients' sexual partners of the client's HIV positive status if the client does not disclose this information to those with whom they have unprotected sex.
Duty to warn is also quite controversial, as the circumstances aren't always as straightforward as they were in the original Tarasoff case, during which a therapist's client laid out a specific plan to kill an identified person and then followed through with their plan after the session.
In your exam, you may have to recall the name of this rule (Tarasoff), its clinical mandate (duty to warn), or how to apply it in clinical practice.
The rule is also an interesting case study in state-by-state variation of laws that govern therapeutic practice.
Bonus points: What is a state-specific law you have to keep in mind when you work with clients?