A person or entity who is not a party to a lawsuit generally may intervene in the lawsuit and become a party to it by filing a plea in intervention prior to the entry of the court’s judgment—provided the court does not reject (strike) the intervention. An intervenor is not required to secure the court’s permission to intervene, and the party who opposed the intervention has the burden to challenge it by filing a motion to strike.

A person or entity has a right to intervene if the intervenor could have brought the same lawsuit, or any part of it in his own name—or, if the action had been brought against him, he would be able to defeat the lawsuit, or some part of it.

A trial court abuses its discretion by striking an intervention if (1) the intervenor meets the above test, (2) the intervention will not complicate the case by an excessive multiplication of the issues, and (3) the intervention is almost essential to effectively protect the intervenor’s interest.

In Delaware, the rules regarding intervention in a lawsuit are governed by the Delaware Court Rules, specifically the Rules of Civil Procedure. According to these rules, a non-party to a lawsuit may intervene in the case by filing a motion to intervene, typically before the final judgment is entered. The right to intervene is granted if the potential intervenor has an interest that could have led them to initiate the same lawsuit or defend against it. The intervenor does not need to obtain permission from the court to file the motion, but the party opposing the intervention can challenge it by filing a motion to strike the intervention. The court will consider whether the intervenor meets the criteria for intervention, whether the intervention will unduly complicate the case, and whether the intervention is necessary to protect the intervenor's interests. If a trial court strikes an intervention without proper consideration of these factors, it may be seen as an abuse of discretion. An attorney can provide specific guidance on the process and likelihood of success for intervention in a particular case in Delaware.