In what circumstances will a jury overturn a conviction for receiving stolen property?

In People v. Dupre, supra, 262 Cal.App.2d 56, the defendant was found in possession of recently stolen property. The question was whether she knew at the time that the property was stolen. She gave a rational explanation for how she came by the property honestly. There was no evidence to suggest that she knew it was stolen. Her conviction for receiving stolen property was properly reversed: "A jury is not altogether free to reject as `unsatisfactory' whatever explanation the defendant gives. There must be some flaw in the explanation itself, or it must be discredited by other evidence. Otherwise the jury would, in effect, be authorized to convict upon proof of possession irrespective of what explanation had been made." (Id. at p. 60.)