What is the test for establishing constitutionally inadequate assistance of counsel?

establishing constitutionally inadequate assistance of counsel. [Citations.] If the record on appeal sheds no light on why counsel acted or failed to act in the manner challenged, an appellate claim of ineffective assistance of counsel must be rejected unless counsel was asked for an explanation and failed to provide one, or there simply could be no satisfactory explanation. [Citation.]' " (People v. Gamache (2010) 48 Cal.4th 347, 391.) A reviewing court presumes that counsel's performance fell within the wide range of professional competence and that counsel's actions and inactions can be explained as a matter of sound trial strategy.

The "review of counsel's performance is to be highly deferential.... 'Because of the difficulties inherent in making the evaluation [of counsel's tactical choices], a court must indulge a strong presumption that counsel's conduct falls within the wide range of reasonable professional assistance; that is, the defendant must overcome the presumption that, under the circumstances, the challenged action "might be considered sound trial strategy." [Citation.] There are countless ways to provide effective assistance in any given case. Even the best criminal defense attorneys would not defend a particular client in the same way____' [Citation.]" (People v. Duncan (1991) 53 Cal.3d 955, 966.)