The physician patient privilege protects the communications a patient makes to the doctor from disclosure in court. The rationale behind this privilege is to encourage patients to be truthful in order to obtain the best and most accurate diagnoses.
Physician Patient Privilege in the United States
Neither the Federal Rules of Evidence nor common law recognizes the physician patient privilege. Instead, such a privilege is statutory in nature. New York was the first state to enact a physician patient privilege statute in 1828. Most states allow at least a limited privilege to communications between physician and patient. These statutes give the patient the privilege against the disclosure in court of:
- confidential communications
- made to a physician
- if made for the purpose of obtaining treatment or diagnosis looking towards treatment.
The privilege belongs to the patient, not the doctor. This privilege will only cover information given to a doctor for the purposes of obtaining treatment or diagnosis and not for any other type of consultations.
The physician patient privilege may be waived either directly by the patient, or if the patient's medical condition or information is "put in issue" by the case. However, even when an individual's mental or physical condition is in issue, courts generally will construe the waiver as narrowly as they can, for the protection of the patient.
- Patient Litigant exception- Many statutes have an exception for "patient-litigant" situations, in which a patient is a litigant in the suit and has put her medical condition in issue. Because the medical condition is at issue, the physician patient privilege is waived.
- Public Safety exception- If a physician believes that a patient may be dangerous to others, several state statutes allow him to disregard the patient's privilege and warn the authorities, as well as the victim(s).
Psychotherapist Patient Privilege
A physician may include a psychiatrist. The psychotherapist-patient privilege is more widely accepted than physician patient privilege as all but one of the states recognize some form of psychotherapist-patient privilege. The rational behind this privilege is that promising confidence to a psychotherapy patient gives them an incentive to consult and trust the therapists. This is particularly important as individuals who do not receive mental treatment may commit crimes without such therapy. The same exceptions apply to this privilege as to the physician patient privilege. In addition, some courts allow the victim of violence by the patient to sue the patient's therapist if the patient communicated to the therapist an intent to harm the victim and the therapist unreasonably failed to do so.
A closely related concept to the physician patient privilege is the idea of medical confidentiality. While the physician patient privilege applies only in the courtroom, medical confidentiality applies to all contexts beyond litigation. This concept applies to information shared by the patient with the physician and prevents the physician from sharing such information with any third parties. Medical confidentiality is based on ethics rather than law.
The UK has a system of testimonial compulsion- meaning that a physician, though bound by ethics to keep a patient's confidentiality, must disclose such information to a court if ordered to do so. In the first case to address the physician patient privilege, Duchess of Kingston's Case, the House of Lords asserted:
If a surgeon was voluntarily to reveal these secrets, to be sure he would be guilty of a breach of honour and of great indiscretion; but, to give that information in a court of justice, which by the law of the land he is bound to do, will never be imputed to him as any indiscretion whatever.
Thus, there is not statutory physician-patient privilege in British civil or criminal law. The judge, however, does have the right to allow physicians to refuse disclosure of information that may result in a breach of an ethical duty and the information is not crucial to the case at hand. Like in the United States, in the British and Commonwealth jurisdictions, the privilege belongs to the patient, not the physician.
European Court of Justice
There is the concept of physician-patient confidentiality in all member states but each member state has varying limits to that confidentiality.
In France, the physician-patient privilege is referred to as a professional secret. Medical privilege is held by the professional rather than the patient. This privilege is absolute, meaning that it cannot be waived. However, the concept of absolute privilege has only been upheld in criminal cases.The civil branch of the Cour de Cassation has permitted waiver of the professional secret when the waiver is in the patient's best interest. Furthermore, though violation of the professional secret originally required malicious intent, it now only requires intentional conduct. Penal Code (1810), article 378- Doctors, surgeons and other health officials, including pharmacists, nurses, and all other "bailees of secrets and confidences communicated" by their status or profession, who will reveal those secrets, in all instances other than when the law compels them to disclose, will be punished with a term of no less than one month and no more than six months of imprisonent, and a fine of 100-500 francs. 
Swiss Penal Code, article 321 covers violations of the professional secret- Doctors, dentists, nurses, and pharmacists who reveal a professional secret that was made to them in confidence will be subject to parole for three years or more or will be subject to a fine. ("Les eccl�siastiques, avocats, d�fenseurs en justice, notaires, contr�leurs astreints au secret professionnel en vertu du code des obligations, m�decins, dentistes, pharmaciens, sages-femmes, ainsi que leurs auxiliaires, qui auront r�v�l� un secret � eux confi� en vertu de leur profession ou dont ils avaient eu connaissance dans l'exercice de celle-ci, seront, sur plainte, punis d'une peine privative de libert� de trois ans au plus ou d'une peine p�cuniaire. Seront punis de la m�me peine les �tudiants qui auront r�v�l� un secret dont ils avaient eu connaissance � l'occasion de leurs �tudes. La r�v�lation demeure punissable alors m�me que le d�tenteur du secret n'exerce plus sa profession ou qu'il a achev� ses �tudes.")
Belgian Penal Code, article 458, illustrates the professional secret in a manner that emphasizes the importance of testimonial compulsion- Doctors, surgeons, health officers, pharmacists, nurses, and all other "bailees of secrets and confidences communicated" by their status or profession, who have confidentiality information that they reveal outside of court or legally compelled testimony, will be subject to imprisonment from eight days to six months and be subject to a fine. ("Les m�decins, chirurgiens, officiers de sant�, pharmaciens, sages-femmes et toutes autres personnes d�positaires, par �tat ou par profession, des secrets qu'on leur confie, qui, hors le cas o� ils sont appel�s � rendre t�moignage en justice (ou devant une commission d'enqu�te parlementaire) et celui o� la loi les oblige � faire conna�tre ces secrets, les auront r�v�l�s, seront punis d'un emprisonnement de huit jours � six mois et d'une amende de cent [euros] � cinq cents [euros].") 
Medical privilege exists in 3 states: Tasmania, the Northern Territory, and Victoria. In these jurisdictions, privilege is limited to civil cases.
Tasmania: "(1) A medical practitioner, without the consent of his or her patient, must not divulge in any civil proceeding any communication made to him or her in a professional capacity by the patient that was necessary to prescribe or act for the patient unless the sanity of the patient is the matter in dispute. (2) A person who has possession, custody or control of any communication referred to in subsection (1) or of any record of such a communication made to a medical practitioner by a patient, without the consent of the patient, must not divulge that communication or record in any civil proceeding unless the sanity of the patient is the matter in dispute."
Victoria: "No physician or surgeon shall without the consent of his patient divulge in any civil suit action or proceedings (unless the sanity or the testamentary capacity of the patient is the matter in dispute) any information which he has acquired in attending the patient and which was necessary to enable him to prescribe or act for the patient." 
Northern Territory: "A medical practitioner shall not, without the consent of his patient, divulge in any civil proceeding (unless the sanity of the patient is the matter in dispute) any communication made to him in his professional character by the patient, and necessary to enable him to prescribe or act for the patient." 
Though the physician-patient privilege started out as applying only to civil cases, in 1980, New Zealand extended it to criminal proceedings as well. In order to qualify as privileged in criminal cases, the communication needs to meet the requirements for privilege in civil cases, and also show that the purpose of the communication was to enable the doctor to examine, treat or act for the patient for (a) drug dependency or (b) any other condition or behavior that manifests itself in criminal conduct. The Evidence Act of 2006 reaffirms this notion.
Quebec: The Quebecois statute provides that "No physician may be compelled to declare what has been revealed to him in his professional character." 
Like the UK, testimonial compulsion is applicable. National Health Act section 14-
- All information concerning a user, including information relating to his or her health status, treatment or stay in a health establishment, is confidential.
- Subject to section 15, no person may disclose any information contemplated in subsection (1) unless:a. The user consents to that disclosure in writing; b. A court order or any other law requires that disclosure; or c. Non-disclosure of the information represents a serious threat to public heath. 
See also Evidence
- Daniel W. Shuman, The Origins of Physician Patient Privilege and Professional Secret, 39 Sw. L. J. 661 (1985).
- Shuman, footnote 1. See also New York City Health and Hospitals Corporation v. Morgenthau (In the Matter of Grandy Jury Investigation in New York County), 2002 NYU int. 113, available at https://www.law.cornell.edu/nyctap/I02_0113.htm
- Doe v. Diamond, 964 F.2d 1325 (2d Cir. 1992)
- Tarasoff v. Regents of University of California, 551 P.2d 334 (Cal 1976).
- Rex v. Duchess of Kingston, 20 How. St. Tr. 355, 572-572 (1776).
- Law Reform Committee (London) Privilege in Civil Proceedings 20-22 (Sixteenth Report 1967).
- Daniel W. Shuman, The Origins of Physician Patient Privilege and Professional Secret, 39 Sw. L. J. 661 (1985).
- Miss M. v. Commission, Case 155/78, E. Comm. Ct. J. Rep. 1797 (1980).
- Evidentiary Privileges in International Arbitration, Mosk and Ginsburg, The International and Comparative Law Quarterly, Vol 50, No. 2 (Apr 2001) 345-385, 354.
- Daniel W. Shuman, The Origins of Physician Patient Privilege and Professional Secret, 39 Sw. L. J. 661, Note 1(1985).
- French Criminal Code- available at http://www.napoleon-series.org/research/government/france/penalcode/c_penalcode3b.html
- Swiss Criminal Code- available at http://www.admin.ch/ch/f/rs/311_0/a321.html.
- Belgian Criminal Code- available at http://www.ejustice.just.fgov.be/loi/loi.htm.
- Tasmania Evidence Act 2001, section 127A, available at http://www.austlii.edu.au/au/legis/tas/consol_act/ea200180/s127a.html.
- Victoria Evidence Act 1958, section 28, available at http://www.austlii.edu.au/au/legis/vic/consol_act/epa1958361/s28.html.
- Northern Territory Evidence Act, section 12, available at http://www.austlii.edu.au/au/legis/nt/consol_act/ea80/s12.html.
- New Zealand Evidence Act 2006 No 69, Part 2, Subpart 8 (59)(2), available at http://www.legislation.govt.nz/act/public/2006/0069/latest/DLM393667.html.
- Quebec Rev. Stat. (1941).
- Medical Professional secrecy with Special Reference to Venereal Diseases, Bernfeld, British Journal of Venereal Disease 43, 53 (1967).
- Ethics roundtable debate: Is a physician-patient confidentiality relationship subservient to a greater good? Arthur Morgan, Critical Care 25 April 2005.