In State v. Sartin, 200 Wis. 2d 47, 546 N.W.2d 449 (1996), the supreme court concluded that, in a possession of controlled substance case: "The only knowledge that the State must prove beyond a reasonable doubt ... is the defendant's knowledge or belief that the substance was a controlled or prohibited substance. The State is not required to prove the defendant knew the exact nature or precise chemical name of the substance." Id. at 61. Further, to the extent that "the nature of the controlled substance" may be material at all, it is "only material to the determination of the penalty to be applied upon conviction." Id.