Res judicata and collateral estoppel are two very important legal concepts which often arise and which few pro se litigants understand.

We are gradually going to add additional articles to LessonsInLaw.com on more complex and/or specific legal topics rather than just on general issues as to representing yourself in court (aka pro se or pro per).

On these topics, the reader will need to understand we will be discussing the legal issues but each state will have their own, specific laws on the topic and these articles are designed to provide an overall concept of the topic, not specific to any state. Additional research must be done on the laws in their state if these issues actually arise in their case.

Res judicata and collateral estoppel are close to being the same thing and are often confused. However, the minor differences have a major effect.

The initial concept to understand is these two issues are important is they are used to provide finality to an issue or claim.

Res Judicata

Res judicata literally translates as "a matter judged". It is a defensive issue that is raised to state a claim is precluded from being pursued because it has already been decided by a court and a resolution has been reached. 

Three Elements of Res Judicata

1. There must have been a prior action in which the same claims were or could have been raised;
2. The parties in the second litigation must be identical as those in the first case or in privity with those in the first case (privity is an issue for a different article); and
3. There must have been a final judgment on the merits in the first case (this one is a little tricky, since a settlement that disposes of all issues can also be considered a final judgment on the merits).

Collateral Estoppel

Collateral estoppel prevents subsequent litigation of legal determinations of fact and law that have resulted in valid final judgments. The key distinction between Collateral Estoppel and Res Judicata can be summed up as:

Res Judicata is about claims not being relitigated and Collateral Estoppel is about issues not being relitigated.

If an issue has already been litigated and decided in a case then collateral estoppel states that the same issue has already been decided in any subsequent cases that involve the same issue.

Three Elements of Collateral Estoppel

1. There must have been a prior case in which the same, identical issue was heard by the court;
2. The issue must have actually been litigated with the side who tries to bring the claim again later actually having an opportunity to present a full and fair case on their behalf on the issue; and
3. The issue must have been decided and a decision rendered on it as a necessary part of the judgment of the court.

A key difference between collateral estoppel and res judicata is that collateral estoppel does not address issues that could have been raised and were not.