Generally, ineffective assistance of counsel claims are preserved for postconviction to allow trial counsel an opportunity to defend the charge. State v. Mulder, 313 N.W.2d 885, 890 (Iowa 1981). We depart from this preference if the record on direct appeal is sufficient to evaluate the merits of a defendant's ineffective assistance of counsel claim. Id. If not, we preserve the claim for postconviction proceedings so the facts may be developed. State v. Koenighain, 356 N.W.2d 237, 238 (Iowa App. 1984). Our review of an allegation of ineffective assistance of counsel is de novo. State v. Howes, 525 N.W.2d 874, 876 (Iowa App. 1994). A defendant has the burden of proving by a preponderance of the evidence his attorney did not perform an essential duty and, as a result, he was prejudiced. State v. Howell, 557 N.W.2d 908, 913 (Iowa App. 1996). to demonstrate prejudice, a defendant must prove there is a reasonable probability that but for counsel's unprofessional error, the result of the proceeding would have been different. State v. Atwood, 602 N.W.2d 775, 784 (Iowa 1999). A reasonable probability is one sufficient to undermine confidence in the outcome. State v. Carrillo, 597 N.W.2d 497, 500 (Iowa 1999).