What is the test for a plaintiff to succeed in a claim for malpractice?

To prevail, defendant must show her attorney acted below the standards of professional care and there is a reasonable probability she would have obtained a better result in the absence of counsel's failings. (People v. Ledesma (1987) 43 Cal.3d 171, 217-218.) However, " 'In some cases . . . the record on appeal sheds no light on why counsel acted or failed to act in the manner challenged. In such circumstances, unless counsel was asked for an explanation and failed to provide one, or unless there simply could be no satisfactory explanation, these cases are affirmed on appeal.' " (Id. at p. 218.)