A more thorough explanation:

Declaration against interest is a statement made by someone who is not available to testify in court. The statement is against their own financial, property, or legal interests when it was made. This type of statement is an exception to the hearsay rule, which usually prevents out-of-court statements from being used in court because they may not be trustworthy.

The reason why a declaration against interest is an exception to the hearsay rule is that people usually do not say things that are against their interests unless they are true. Policymakers allow this exception because these statements can be important in cases where a witness is not available to testify.

In order for a statement to be considered a declaration against interest, it must meet certain requirements. First, the person who made the statement must not be available to testify in court. Second, the statement must be harmful to the person who made it or helpful to the other party in the case. Lastly, in a criminal case, there must be other evidence that makes the statement more trustworthy.

For example, if someone said that they had been drinking before they got into a car accident, that statement would be against their own interests in a driving under the influence case. This type of statement could be used as evidence in court if the person who made the statement is not available to testify.

Another example would be if someone wrote a letter admitting to a crime and then died before the trial. The letter could be considered a declaration against interest and could be used as evidence in court.

Overall, a declaration against interest is a statement made by someone who is not available to testify in court that is against their own interests when it was made. This type of statement is an exception to the hearsay rule and can be used as evidence in court if it meets certain requirements.