In People v. Bray (1975) 52 Cal.App.3d 494, the defendant pleaded guilty in Kansas to being an accessory before the fact and was placed on two years probation. (Bray at p. 496.) He subsequently sought to register to vote and filled out a form indicating he was uncertain whether he had been convicted of a felony; he was permitted to vote. (Ibid.) He sought employment as a security guard and stated he had not been convicted of a felony, but explained the prior offense; the Bureau of Collection and Investigative Services registered him as a guard. (Ibid.) Under those unusual circumstances, the appellate court ruled that it was error not to instruct upon mistake of fact, but cautioned that it was "only in very unusual circumstances such as these that the giving of these instructions is necessary." (Id. at p. 499.)