1421390 (June 20, 2005) (defense counsel's failure to examine file on defendant's prior conviction for rape and assault at sentencing phase of capital murder trial fell below the level of reasonable performance, and such failure was prejudicial to defendant, warranting habeas relief on grounds of ineffective assistance of counsel, placing reliance on ABA Standards, which stated: "It is the duty of the lawyer to conduct a prompt investigation of the circumstances of the case and to explore all avenues leading to facts relevant to the merits of the case and the penalty in the event of conviction. The investigation should always include efforts to secure information in the possession of the prosecution and law enforcement authorities. The duty to investigate exists regardless of the accused's admissions or statements to the lawyer of facts constituting guilt or the accused's stated desire to plead guilty." 1 ABA Standards for Criminal Justice 4-4.1 (2d ed. 1982 Supp.). The Court stated: ""[W]e long have referred [to these ABA Standards] as 'guides to determining what is reasonable.' " Wiggins v. Smith, 539 U.S., at 524, 123 S.Ct. 2527 (quoting Strickland v. Washington, 466 U.S., at 688, 104 S.Ct. 2052), and the Commonwealth has come up with no reason to think the quoted standard impertinent here." (Id. at 2466)).