Mass. R. Evid. 806
When a hearsay statement has been admitted in evidence, the declarant's credibility may be attacked, and then supported, by any evidence that would be admissible for those purposes if the declarant had testified as a witness. The court may admit evidence of the declarant's inconsistent statement or conduct, regardless of when it occurred or whether the declarant had an opportunity to explain or deny it. If the party against whom the statement was admitted calls the declarant as a witness, the party may examine the declarant on the statement as if on cross-examination.
Mass. Guid. Evid. 806
This section is taken from Commonwealth v. Mahar, 430 Mass. 643, 649 (2000), in which the Supreme Judicial Court "accept[ed] the principles of proposed [Mass. R. Evid.] 806." See Commonwealth v. Gray, 463 Mass. 731, 748 & n.17 (2012) (quoting with approval Mass. G. Evid. § 806 and ruling that grand jury testimony of unavailable witness Jamison, who identified photograph of person other than defendant as perpetrator, was erroneously precluded to impeach witness's testimony at trial that Jamison had identified defendant). See also Commonwealth v. Pina, 430 Mass. 66, 76 (1999) ("We now adopt the rule in the circumstances of this case."); Commonwealth v. Sellon, 380 Mass. 220, 224 n.6 (1980).