When it becomes necessary for the purposes of this article to determine whether a child who participated in sexual conduct was younger than eighteen years of age, the court or jury may make this determination by any of the following methods:
(1) personal inspection of the child;
(2) inspection of the photograph or motion picture that shows the child engaging in the sexual performance;
(3) oral testimony by a witness to the sexual performance as to the age of the child based on the child's appearance at the time;
(4) expert medical testimony based on the appearance of the child engaging in the sexual performance; or
(5) any other method authorized by law or by rules of evidence.