I heard that guy on FNC too. He said a few states in this country have the same law, but it's rare.
Parent has to testify as to what he "saw". So if Papa Sloot saw Nat's body lying in bushes, he has to say. If mama Sloot saw freshly laundered clothes of Jorans, she has to say. If Joran never touched a washing machine prior to this, she has to say.
you can find out alot by what the mama saw in my opinion.