Declaration Against Interest
Definition - What does Declaration Against Interest mean?
A declaration against interest is a statement made by a witness that would normally be inadmissible due to the hearsay rule, but that is admissible because it is completely against the persons's own interests.
For a declaration against interest to be legitimate, the witness must be unavailable or unable to testify in court.
Justipedia explains Declaration Against Interest
The reason why declarations against interest are admissible when other declarations may be inadmissible due to hearsay is because the court assumes that if a person is willing to make a statement that humiliates or incriminates themselves, or otherwise works against their interest, then there is no reason for the person to lie.
However, even if a declaration of interest is allowed to be used as evidence, the jury will still have to decide whether or not they believe it to be true.