The legal system has determined that an expert witness in developing an opinion can apply different levels of technical methodology. In some cases the courts have decided that “junk science” was used to develop an expert opinion and has not allowed the jury to hear such opinions. Courts at all levels, federal and state, have adopted criteria used to judge the admissibility of expert testimony. To evaluate technical reliability the courts use the landmark cases Frye and Daubert. This presentation will explain how the courts apply these rulings as gate keeping techniques to avoid allowing poor or junk science into the courtroom and it will discuss the key elements needed to pass the test of technical reliability.