What is the test for proving actual malice in a defamation case?

" 'Actual malice . . . requires at a minimum that the statements were made with a reckless disregard for the truth. And although the concept of "reckless disregard" "cannot be fully encompassed in one infallible definition," [citation], we have made clear that the defendant must have made the false publication with a "high degree of awareness of . . . probable falsity," [citation], or must have "entertained serious doubts as to the truth of his publication," [citation].' " (Young v. CBS Broadcasting, Inc. (2012) 212 Cal.App.4th 551, 562-563.) Failure to investigate, anger or hostility, or reliance on unreliable sources, may indicate a defendant's doubt about a statement's truth, but these factors are only relevant in context. Mere proof of ill will is not malice. Nor is the mere failure to conduct a thorough investigation. (Id. at p. 563.)