To the contrary, under the Rules the trial judge must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable. The Court in Daubert pointed to a number of factors that might indicate the scientific evidence was reliable. Among them were whether the scientific technique can be tested, its known rate of error, whether standards exist to control its operation, its general acceptance in the field, and the possibility the evidence would overwhelm, confuse, or mislead the jury. The general acceptance test became just one of several factors. Since Daubert merely interpreted the Federal Rules, the case only applied to federal courts.
Most criminal trials take place in state courts, which are governed by state evidence codes.
Many state legislatures have left the decision over admissibility of scientific evidence to the courts. Some have adopted codes resembling the Federal Rules. Several legislatures have enacted laws banning specific controversial techniques, such as lie detector tests, from being presented in evidence. In short, many state courts still follow the Frye test, others follow Daubert , and others follow legislative bans on scientific evidence. The lie detector, or polygraph, is based on the idea that, when people lie, their body reacts in ways that they cannot control.