Subject to numerous limitations and exceptions, evidence probative of the credibility of a witness is admissible to impeach the witness.

Cf. United States v. Gonzales, 436 F.3d 560, 578-579 (5th Cir. 2006) (holding that the defendants' "compulsory process rights were not plainly violated by the government's failure to produce deported witnesses," considering that....The prohibition, grounded in the Compulsory Process Clause, against deliberate government action that deprives a criminal defendant of the relevant and material exculpatory testimony of a witness may effectively limit the government's use of hearsay evidence against a criminal defendant.

Cf. United States v. Lawrence, 349 F.3d 109, 117 (3d Cir. 2003) (upholding trial court's exclusion into evidence of the victim's hospital bed identification of another suspect as a dying declaration because defendant failed....The hearsay exception for dying declarations applies only if the declarant believed that his or her own death was imminent when he or she made the statement.

Cf. Carrion v. Smith, 549 F.3d 583, 590 (2d Cir. 2008) (habeas corpus petition based on claim of ineffective assistance of counsel; trial judge rejected some of magistrate's findings of fact; "We are concerned about another aspect of the district court's finding of facts. Judge Scheindlin suggests...If behavior is largely volitional rather than semi-volitional or semi-automatic, it is hot habit.