A more thorough explanation:

Misjoinder refers to the improper joining of a party to a criminal or civil lawsuit.

In federal civil cases, misjoinder occurs when a party is joined to a case in violation of permissive joinder under Federal Rules of Civil Procedure Rule 20. This means that the alleged claim against them does not arise out of the same transaction or occurrence as other defendants, and there are no common questions of law or fact.

For example, if a plaintiff sues a company for breach of contract and also includes an unrelated claim against an individual employee of the company, that employee may be considered misjoined.

In federal criminal cases, misjoinder occurs when a defendant is charged with an offense that is not of the same character, based on the same act or transaction, or connected with a common scheme as other defendants.

For example, if several individuals are charged with drug trafficking, but one defendant is also charged with tax evasion unrelated to the drug trafficking, that defendant may be considered misjoined.

In addition, under Federal Rules of Criminal Procedure 14(a), a court may order separate trials or grant a severance of defendants if joining a defendant in a case would unfairly prejudice any of the parties.

Overall, misjoinder can lead to confusion and unfairness in legal proceedings, and it is important to ensure that parties are properly joined to a case based on their involvement and connection to the alleged claims.