Things done in one action cannot be taken as evidence in another, unless it be between the same parties.

Explanation

(English-origin maxim.) Proceedings and findings in one action cannot serve as evidence in a different action unless both actions involve the same parties, because strangers to the first case had no opportunity to test the evidence.

Where this applies

• A plaintiff tries to introduce the verdict from a lawsuit between two other people as proof in his own case — the court excludes it because he wasn't a party to the first action and the other side had no chance to cross-examine on his behalf.
• A company sues a supplier and wants to use findings from a regulatory investigation the supplier faced — the court won't allow it because the company wasn't a party to that investigation.
• A defendant in a fraud case tries to show that a different jury found a key witness unreliable in a separate trial — the court excludes it because the parties in the two cases are different.