In United States law, a statement against interest is a statement made by a person which places them in a less advantageous position than if they had not made the statement and is as a consequence deemed credible as evidence (usually within a legal trial). For example, if a driver in an automobile accident boasts publicly that they were speeding, it may represent a legal admission of liability. It is analogous to the criminal equivalent, the statement against penal interest which is a statement that puts the person making the statement at risk of prosecution. Statements against interest by parties not present at a trial may be admitted as evidence where in other circumstances they would be excluded as hearsay.
Under the Federal Rules of Evidence, Rule 804(b)(3) provides:
"A statement that:
(A) a reasonable person in the declarant’s position would have made only if the person believed it to be true because, when made, it was so contrary to the declarant’s proprietary or pecuniary interest or had so great a tendency to invalidate the declarant’s claim against someone else or to expose the declarant to civil or criminal liability; and
(B) is supported by corroborating circumstances that clearly indicate its trustworthiness, if it is offered in a criminal case as one that tends to expose the declarant to criminal liability." See Fed. R. Evid. 804(b)(3). The rule was last amended on December 1, 2010. See Legislative History (with links to key documents).