 Warren concluded that the nature of the Texas law at issue denied Washington the right for a fair trial using witnesses who could testify to " relevant and material " facts in the case . Here , while not entirely relying on the finding , the Court saw the law as " arbitrary " because its discrimination between the prosecution and defense served " no rational relationship " to any goal of preventing perjury . Further , the idea that a " competent " witness was barred from testifying , in and of itself , was held to be an unconstitutional predetermination on the part of the state legislature . The Court 's decision upheld the importance of juries in evaluating the truth and credibility of witnesses ' statements . 
