In what circumstances will collateral estoppel prevent a defendant from a conviction for murder in the second degree?

In Summersville, the issue was whether collateral estoppel precluded the defendant's conviction for murder in the second degree on a theory of aiding and abetting after the principal was convicted of first degree murder. (People v. Summersville, supra, 34 Cal.App.4th at p. 1065, 40 Cal.Rptr.2d 683.) The court's only comment concerning the nature of a conviction was in determining whether the defendant's coaccused's conviction was a final judgment on the merits to which collateral estoppel would apply. "First, as [the coaccused's] appeal is still pending, there is no final judgment on the merits." (Id. at p. 1068, 40 Cal.Rptr.2d 683.)