Section 263.25. Proof of age of child

Whenever  it  becomes  necessary  for  the purposes of this article to
  determine whether a child who participated in a sexual  performance  was
  under  an age specified in this article, the court or jury may make such
  determination by any of the following: personal inspection of the child;
  inspection of a photograph  or  motion  picture  which  constituted  the
  sexual   performance;   oral  testimony  by  a  witness  to  the  sexual
  performance  as  to  the  age  of  the  child  based  upon  the  child's
  appearance;  expert  medical  testimony based upon the appearance of the
  child in the sexual performance; and any other method authorized by  any
  applicable provision of law or by the rules of evidence at common law.