What are the elements of the possession of a controlled substance under the California Controlled Substitute Act?

The elements of the latter offense are (1) possession of a controlled substance, (2) in a prison or jail, (3) knowledge of its presence, (4) knowledge of its nature as a controlled substance, and (5) an amount sufficient for use. (See People v. George (1994) 30 Cal.App.4th 262, 277.) Although lack of authorization is mentioned in the statute, this is not considered an element of the offense. Rather, authorization is an affirmative defense. (Id. at p. 275.)