What is the test for ineffective counsel in criminal proceedings?

"Under both the Sixth Amendment to the United States Constitution and article I, section 15, of the California Constitution, a criminal defendant has the right to the assistance of counsel." (People v. Ledesma (1987) 43 Cal.3d 171, 215.) "In order to demonstrate ineffective assistance of counsel, a defendant must first show counsel's performance was 'deficient' because his 'representation fell below an objective standard of reasonableness . . . under prevailing professional norms.' [Citations.] Second, he must also show prejudice flowing from counsel's performance or lack thereof. [Citations.]

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Prejudice is shown when there is a 'reasonable probability that, but for counsel's unprofessional errors, the result of the proceeding would have been different. A reasonable probability is a probability sufficient to undermine confidence in the outcome.' [Citations.]" (People v. Jennings (1991) 53 Cal.3d 334, 357; see Strickland v. Washington (1984) 466 U.S. 668, 687-688.)