Sears v. Upton

Attorney: right to competent counsel: we rejected any suggestion that a decision to focus on one potentially reasonable trial strategy—in that case, petitioner’s voluntary confession—was “justified by a tactical decision” when “counsel did not fulfill their obligation to conduct a thorough investigation of the defendant’s background.” 529 U. S., at 396;  moreover, the reasonableness of the theory is not relevant when evaluating the impact of evidence that would have been available and likely introduced, had counsel completed a constitutionally adequate investigation before settling on a particular mitigation theory. This point was also plain in Williams: “Whether or not . . . omissions [in the investigation] were sufficiently prejudicial to have affected the outcome of sentencing,” they may nevertheless demonstrate deficiency. 529 U. S., at 396. The one inquiry, deficient mitigation investigation, is distinct from the second, whether there was prejudice as a result; (…) and, in Porter, we recently explained: “To assess [the] probability [of a different outcome under Strickland], we consider the totality of the available mitigation evidence—both that adduced at trial, and the evidence adduced in the habeas proceeding—and reweigh it against the evidence in aggravation.” 558 U. S., at ____ (slip op., at 11) (U.S. S. Ct., 29.06.10, Sears v. Upton, Per Curiam).

Avocat : droit à un conseil compétent : viole son devoir de diligence l'avocat qui ne se base que sur les aveux de son client pour bâtir sa stratégie de défense, sans conduire d'investigations approfondies des circonstances de l'affaire. Même si les omissions dans les investigations n'auraient pas affectées le résultat de la procédure pénale, ces omissions n'en demeurent pas moins constitutives d'une violation du devoir de diligence. Enfin, en évaluant la probabilité d'un résultat différent au sens de la jurisprudence Strickland, la Cour considère la totalité des circonstances atténuantes disponibles (aussi bien celles résultant du procès principal que de la procédure d'habeas), ces circonstances étant comparées aux circonstances aggravantes.