Texas courts interpret the law based on evidence. In 1998 the Supreme Court of Texas adopted rules of evidence that required experts to testify according to scientific standards rather than just stating their opinions.

These rules are often referred to as The Daubert Standard after the federal case Daubert_v._Merrell_Dow_Pharmaceuticals.

Among other features, evidence presented under The Daubert Standard must comply with the scientific method. It must be obtained through methods that produce repeatable results. The results must be falsifiable.

In practice that means that in Texas courts a shaman cannot present himself as an expert and testify, "Frank is a witch." To which Frank would respond, "No I'm not." The judge seeing the Shaman's many brightly colored feathers would rule that Frank is in fact a witch.

This cannot happen in Texas, at least it is not supposed to happen.

Links relating to the above:

http://en.wikipedia.org/wiki/Daubert_standard - Wikipedia Rules on Daubert Standard

http://en.wikipedia.org/wiki/Daubert_v._Merrell_Dow_Pharmaceuticals - Federal Case

http://cyber.law.harvard.edu/daubert/tx.htm - Judicial Gatekeeping Project in Texas

http://www.thefederation.org/documents/parker.htm - State Variations on Daubert Theme

http://www.texasbar.com/Content/ContentGroups/Publications3/Journal/2001/April2/Robinson_Daubert_and_Mental_Health_Testimony__The_Sky_is_Not_Falling.htm - Analysis from Texas Bar

http://en.wikipedia.org/wiki/Shamanism - Shamanism