What is the test for ineffective assistance of counsel?

To prevail on an ineffective assistance of counsel claim, a defendant must show both (1) "that counsel's representation fell below an objective standard of reasonableness," and (2) "that there is a reasonable probability that, but for counsel's unprofessional errors, the result of the proceeding would have been different." Strickland v. Washington, 466 U.S. 668, 688, 694 (1984).

"If it is easier to dispose of an ineffectiveness claim on the ground of lack of sufficient prejudice . . . that course should be followed." Strickland, 466 U.S. at 697. "A reasonable probability is a probability sufficient to undermine confidence in the outcome." Id. at 694. In evaluating whether the proceeding would have been different but for counsel's error, "[t]he likelihood of a different result must be substantial, not just conceivable." Harrington v. Richter, 562 U.S. 86, 112 (2011).