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 Utah, a person or entity not originally part of a lawsuit may intervene in the case by filing a plea in intervention before the court's judgment is entered. The process does not require the court's permission, and the burden to challenge the intervention lies with the party opposing it, who must file a motion to strike. The right to intervene is granted if the potential intervenor has a significant interest in the lawsuit, such that they could have initiated the same lawsuit themselves or would have a defense against it if they were sued. The court may only strike an intervention if it fails to meet the criteria of having a substantial interest in the case, if it excessively complicates the case by adding too many issues, or if the intervention is not crucial for protecting the intervenor's interests. Striking an intervention that meets these conditions could be considered an abuse of discretion by the trial court.