A more thorough explanation:

Forfeiture by wrongdoing is a legal term that allows a statement made by a person who is not present in court to be admitted as evidence. This statement is usually considered hearsay and would not be admissible in court. However, if the person who made the statement is unavailable to testify because of the intentional or wrongful actions of the opposing party, the statement can be admitted under the forfeiture by wrongdoing exception to the hearsay rule.

For example, if a defendant in a criminal case threatens a witness to prevent them from testifying, the witness's previous statement to the police or in a deposition may be admitted as evidence under the forfeiture by wrongdoing exception.

This exception is also used in cases where a defendant has killed or harmed a witness to prevent them from testifying. In such cases, the defendant forfeits their right to confront the witness against them under the Sixth Amendment.

Overall, forfeiture by wrongdoing is a legal tool that allows courts to admit evidence that would otherwise be inadmissible due to the hearsay rule or the right to confront witnesses. It is used to prevent parties from benefiting from their own wrongful actions that prevent witnesses from testifying.