Is a defendant's reliance on a prior guilty plea in a motion for habeas corpus misplaced?

Defendant's reliance on People v. Shoals (1992) 8 Cal.App.4th 475 is also misplaced, if not moreso. There, the defendant sought a petition for a writ of habeas corpus based on a claim that counsel had rendered ineffective assistance in failing to introduce his co-defendant's guilty plea to possession of drugs that the defendant was also charged with possessing. (Id. at pp. 481, 501.) In declining to issue an order to show cause on that ground, we did not discuss the relevance or admissibility of the codefendant's guilty plea, let alone imply that such evidence was relevant and admissible.