Is a failure to hold a complete inquiry prejudicial?

In People v. Lewis (1978) 20 Cal.3d 496, 499, 143 Cal.Rptr. 138, 573 P.2d 40, the court discussed whether failure to hold a complete inquiry is prejudicial: " 'There can be no doubt it was. On this record we cannot ascertain that defendant had a meritorious claim, but that is not the test. Because the defendant might have catalogued acts and events beyond the observations of the trial judge to establish the incompetence of his counsel, the trial judge's denial of the motion without giving defendant an opportunity to do so denied him a fair trial. We cannot conclude beyond a reasonable [2 Cal.App.4th 1667] doubt that this denial of the effective assistance of counsel did not contribute to the defendant's conviction.' [Citation.]"