Collateral estoppel prevents a prosecutor from bringing up the same issue in successive criminal cases. It functions much like double jeopardy by preventing the relitigation of factual issues.

History
The use of collateral estoppel in criminal cases is of recent origin. Previously, it was believed that the double jeopardy doctrine of the Fifth Amendment would adequately protect defendants from the harassment, expense, and embarrassment of having to defend themselves from multiple charges for the same crime.

However, within the last several decades, it has become apparent that double jeopardy fails to fully protect defendants from relitigation of particular factual issues. Therefore, the U.S. Supreme Court extended the doctrine of double jeopardy to now include collateral estoppel.

Definition
Collateral estoppel is sometimes referred to as the secondary aspect of res judicata, which bars the same parties from litigating a second lawsuit on the same claim. Basically, when collateral estoppel is raised as a defense, you are saying that a particular fact was already decided and the prosecution is estopped (prohibited) from relitigating that issue.

When is it Used?
Collateral estoppel is most often invoked as a defense when multiple crimes can be attributed to one fact pattern. Modern statutes create technical and specific offenses that are usually part of the same act but can be prosecuted in multiple proceedings.

Therefore, collateral estoppel should be raised as a defense when a particular fact was conclusively decided at a previous trial or other formal proceeding.

However, courts can be quite liberal when ruling on a collateral estoppel claim. They may allow the factual issues to be introduced:

• If it's unclear whether a particular issue has been decided
• If it appears that a judge or jury made a decision on the basis of something that was not at issue in the trial

In these instances, the court will usually rule that the prosecution is not collaterally estopped from bringing up the factual issue because it was not conclusively decided.