Interesting discussions here; http://legallad.qdnow.com/2007/06/01/confidentiality.aspx
Under general principles of tort law, no one has a duty to protect people from the violent acts of others. However, in some limited situations, you can be held responsible for the acts of people with whom you have a special relationship. In the landmark case of Tarasoff v. Regents of University of California, the California Supreme Court held that the special relationship between a psychotherapist and a patient imposes on the therapist a duty to act reasonably to protect the foreseeable victims of a patient.
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Ergo: if HK$ was KE’s patient (prescribed Rx for him) she had a duty to warn ANS or LE that he was giving ANS lethal doses of illegally obtained drugs...otherwise, she was part of the hostage team. IMHO;)