What is the test for failure of proof in a grand theft case?

"Ordinarily, the deduction to be drawn from the circumstances shown in evidence is for the trier of facts, but in this instance it is manifest that every fact proven is consistent with the reasonable conclusion that the appellant did not participate in the theft of the automobile. There is, therefore, a failure of proof in particulars necessary to conviction of the crime of grand theft, and the question is one of law for the court." (People v. Flores (1943) 58 Cal.App.2d 764, 769.)