Section 20B. The following words as used in this section shall have the following meanings:—

''Patient'', a person who, during the course of diagnosis or treatment, communicates with a psychotherapist;

''Psychotherapist'', a person licensed to practice medicine, who devotes a substantial portion of his time to the practice of psychiatry. ''Psychotherapist'' shall also include a person who is licensed as a psychologist by the board of registration of psychologists; a graduate of, or student enrolled in, a doctoral degree program in psychology at a recognized educational institution as that term is defined in section 118, who is working under the supervision of a licensed psychologist; or a person who is a registered nurse licensed by the board of registration in nursing whose certificate of registration has been endorsed authorizing the practice of professional nursing in an expanded role as a psychiatric nurse mental health clinical specialist, pursuant to the provisions of section eighty B of chapter one hundred and twelve.

''Communications'' includes conversations, correspondence, actions and occurrences relating to diagnosis or treatment before, during or after institutionalization, regardless of the patient's awareness of such conversations, correspondence, actions and occurrences, and any records, memoranda or notes of the foregoing.

Except as hereinafter provided, in any court proceeding and in any proceeding preliminary thereto and in legislative and administrative proceedings, a patient shall have the privilege of refusing to disclose, and of preventing a witness from disclosing, any communication, wherever made, between said patient and a psychotherapist relative to the diagnosis or treatment of the patient's mental or emotional condition. This privilege shall apply to patients engaged with a psychotherapist in marital therapy, family therapy, or consultation in contemplation of such therapy.

If a patient is incompetent to exercise or waive such privilege, a guardian shall be appointed to act in his behalf under this section. A previously appointed guardian shall be authorized to so act.

Upon the exercise of the privilege granted by this section, the judge or presiding officer shall instruct the jury that no adverse inference may be drawn therefrom.

The privilege granted hereunder shall not apply to any of the following communications:—

(a) If a psychotherapist, in the course of his diagnosis or treatment of the patient, determines that the patient is in need of treatment in a hospital for mental or emotional illness or that there is a threat of imminently dangerous activity by the patient against himself or another person, and on the basis of such determination discloses such communication either for the purpose of placing or retaining the patient in such hospital, provided however that the provisions of this section shall continue in effect after the patient is in said hospital, or placing the patient under arrest or under the supervision of law enforcement authorities.

(b) If a judge finds that the patient, after having been informed that the communications would not be privileged, has made communications to a psychotherapist in the course of a psychiatric examination ordered by the court, provided that such communications shall be admissible only on issues involving the patient's mental or emotional condition but not as a confession or admission of guilt.

(c) In any proceeding, except one involving child custody, adoption or adoption consent, in which the patient introduces his mental or emotional condition as an element of his claim or defense, and the judge or presiding officer finds that it is more important to the interests of justice that the communication be disclosed than that the relationship between patient and psychotherapist be protected.

(d) In any proceeding after the death of a patient in which his mental or emotional condition is introduced by any party claiming or defending through or as a beneficiary of the patient as an element of the claim or defense, and the judge or presiding officer finds that it is more important to the interests of justice that the communication be disclosed than that the relationship between patient and psychotherapist be protected.

(e) In any case involving child custody, adoption or the dispensing with the need for consent to adoption in which, upon a hearing in chambers, the judge, in the exercise of his discretion, determines that the psychotherapist has evidence bearing significantly on the patient's ability to provide suitable care or custody, and that it is more important to the welfare of the child that the communication be disclosed than that the relationship between patient and psychotherapist be protected; provided, however, that in such cases of adoption or the dispensing with the need for consent to adoption, a judge shall determine that the patient has been informed that such communication would not be privileged.

(f) In any proceeding brought by the patient against the psychotherapist, and in any malpractice, criminal or license revocation proceeding, in which disclosure is necessary or relevant to the claim or defense of the psychotherapist.

The provision of information acquired by a psychotherapist relative to the diagnosis or treatment of a patient's emotional condition, to any insurance company, nonprofit hospital service corporation, medical service corporation, or health maintenance organization, or to a board established pursuant to section twelve of chapter one hundred and seventy-six B, pertaining to the administration or provision of benefits, including utilization review or peer review, for expenses arising from the out-patient diagnosis or treatment, or both, of mental or nervous conditions, shall not constitute a waiver or breach of any right to which said patient is otherwise entitled under this section and section thirty-six B of chapter one hundred and twenty-three.