What is the effect of striking or admonishing the jury to disregard inadmissible testimony by a police officer in a sexual assault case?

Although Magill's testimony lacked relevance and was inadmissible, the issue is whether admonishing and instructing the jury was adequate: "Ordinarily, a curative instruction to disregard improper testimony is sufficient to protect a defendant from the injury of such testimony, and, ordinarily, we presume a jury is capable of following such an instruction." (People v. Navarrete, supra, 181 Cal.App.4th at p. 834.)

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In Navarrete, a detective willfully and in bad faith volunteered that the defendant had confessed to the charged crime, committing a lewd act upon a child. The appellate court found striking the testimony and admonishing the jury to disregard it was inadequate because "[a] jury's belief that a defendant may have confessed eviscerates the presumption of innocence" (People v. Navarrete, supra, 181 Cal.App.4th at p. 834) and "even a single reference to an inadmissible confession can be the sort of 'exceptional circumstance' that supports granting a mistrial because a curative instruction cannot undo the prejudice to the defendant." (Id. at p. 836.)