What is the legal test for assessing the contention that a trial attorney's inadequacy has reduced a criminal trial to a "farce and sham"?

It is well settled that the right of a criminal defendant to the assistance of effective counsel is one of constitutional dimension; if it is demonstrated that a trial attorney's inadequacy has reduced a trial to a "farce and sham," the defendant's conviction will be reversed. (People v. Ibarra (1963) 60 Cal.2d 460, 34 Cal.Rptr. 863, 386 P.2d 487.) Following the declaration of this principle in Ibarra, some definitive guidelines have evolved in the case law concerning the proper approach for assessing the contention defendant has made here.