It is a very common practice for lawyers of completeists or civil parties to enter into agreements that protect their communications. Agreements are statements of intent that communication is protected by the Common Interest Doctrine, which extends a lawyer`s privilege to discussions with parties who share a common interest. According to the doctrine, the privilege of a lawyer is not abandoned when such communications take place between parties who share a common legal interest. Common defence privilege does not only protect statements from lawyer to client or from lawyer to lawyer. The privilege also applies to communications addressed to certain agents of a lawyer, including accountants, who have been recruited to support the provision of legal services.  In addition, a person is not a party to the trial to be a party to a joint defence agreement. Common defence privilege also applies to «parties or potential parties having a common interest in the outcome of a given claim.  Only communications which are made within the framework of an ongoing joint venture and which aim to move the undertaking forward are protected.   «As a general rule, no written agreement is required to invoke the common privilege of the defence.»  While «privileges must be interpreted restrictively and extensions should be extended with caution,» the courts have held that a common oral defense agreement may be valid.  Since an implied agency relationship is generally determined on the basis of the potential client`s reasonable perspective, a well-developed joint defence agreement can confirm that the parties agree that there was no intentional attorney-client relationship with the parties for any purpose. As a purely legal matter, the common privilege of the defence is an erroneous name, as it is not in fact an affirmative privilege; rather, it is an exception to the waiver rule. In general, the disclosure of inside and confidential information to third parties constitutes a waiver of privilege. However, those protected by a common defence agreement may avoid renouncing and retain the privilege, notwithstanding the disclosure of confidential information to third parties.
Finally, the courts require that the lien relating to the disclosure disclosed to a third party has not otherwise been set aside. As a general rule, the privilege applies only to communications made after the party has sought legal advice and given a lawyer. In addition, the parties intend to ensure that communications are confidential and do not disclose the information to third parties who are not parties to the existing agreement of common interest. If such differences are not addressed, they may jeopardize all parties to the Joint Defence Agreement. Therefore, an important provision in any common defense agreement is to deal accurately with what happens when a party decides to terminate or abandon it. As soon as an agreement of common interest exists, participants should not deprive each other of communications that they have previously shared in the framework of an agreement of common interest, even if they are now opposed to the process. However, adversity generally does not require participants to disclose privileged communications that have not been shared with other participants. Equally important is the timing and content of the relevant communication. Communications or non-substantial communications that do not normally correspond to the common interest are not protected. Similarly, communications made before the existence of an agreement of common interest are generally not privileged.
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