Whether in corporate transactions, litigation or business disputes, there may be situations in which multiple separate entities seek to enter into a formal relationship to protect their shared interests, even when represented by separate attorneys. If these entities are co-defendants to an ongoing litigation, they may wish to document the joint defense they share and their intent not to waive attorney-client privilege by sharing strategies and resources. For entities who are not involved in litigation, but who share an interest in a legal issue (such as negotiating a transaction or an ongoing lobbying interest), they may desire to document their common interest.
These scenarios are common, but require navigation to ensure effective communication without jeopardizing any legal privileges or immunities. The specifics of joint defense and common interest privileges can vary significantly across jurisdictions, both at the state and federal levels. Some jurisdictions acknowledge these privileges as one and the same, while others see them as different. Despite these differences, lawyers have consistently and successfully employed the use of formal agreements to establish reasonable parameters that courts typically approve of.