How have courts interpreted improvisation on reasonable doubt?

Appellant claims prejudicial error on the authority of a long line of decisions establishing that an impromptu instruction on reasonable doubt is a perilous exercise. (See People v. Garcia (1975) 54 Cal.App.3d 61, 63-68, 126 Cal.Rptr. 275, and cases cited; see also Pen.Code, 1096a.) They also demonstrate, however, that improvisation As such does not command reversal; only prejudicial error does. (See People v. Garcia, supra, at pp. 68-71, 126 Cal.Rptr. 275.)