Scientific evidence is a double-edged sword. On the one hand, scientific evidence works as a good instrument to clarify the truth in the criminal justice system but on the other hand could cause bad results that is not expected. A judge that usually has no scientific background may face great difficulties in dealing with complex area of expertise. Most of all, a court should consider whether a particular science submitted to a criminal process has minimal scientific validity and also take into consideration how the science prove any fact relevant. This judicial consideration of science does not correspond to what is done by scientists. Daubert v. Merrell Dow Pharmaceutical, Inc., decided by the United States Supreme Court shifts the standards of assessing scientific evidence. What is interesting is that the controversy of legal standard of assessment of scientific evidence become more seriously since after the Daubert decision. The most important reason is because the Daubert case contain contradictive factors in its reasoning. The scientific validity can not stand the sharpened attack from criticisms. There is no clear evidence that the legal standard about admissibility and probative force of scientific evidence has come to be settled. The view that scientific evidence is the best way to clarify the truth in criminal process was criticized in two ways. First, participants of criminal process usually do not have qualified scientists who can properly assess science in court. Second, the argument that trash science is widespread in criminal justice system come to get persuasive powers. The criticisms does not come to end for low-quality science but get to the perspective of paradigm shift for scientific evidence. Nonetheless, until now, the belief that science could rescue bad practice and system of criminal justice makes the problems more complex. For the eyes of some Korean scholars, to achieve justice more effectively in criminal justice system, science should be more often used to prove facts in courts. Also, the legal rule that reliability of evidence should rely on scientific validity express the hope for science. What is more necessary now is understanding pros and cons of science, to open up the door more widely to truth in a court. We should reassess every single scientific method and theory in forensic science area. If any error of a science cannot be totally eradicated, the reasonable reformation of criminal process must be the next option.