What is the legal test for ineffective representation of a criminal defendant?

A criminal defendant is guaranteed the right to the assistance of counsel by the Sixth Amendment to the United States Constitution and article I, section 15 of the California Constitution. "The standard for showing ineffective assistance of counsel is well settled. In assessing claims of ineffective assistance of trial counsel, we consider whether counsel's representation fell below an objective standard of reasonableness under prevailing professional norms and whether the defendant suffered prejudice to a reasonable probability, that is, a probability sufficient to undermine confidence in the outcome. [Citations.] A reviewing court will indulge in a presumption 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. Defendant thus bears the burden of establishing constitutionally inadequate assistance of counsel. " ( People v. Gray (2005) 37 Cal.4th 168, 207, 33 Cal.Rptr.3d 451, 118 P.3d 496.)