The Frye standard is critical to the legal presentation of the findings of a forensic examination. Forensic evidence is based on science. Some of the scientific methods have been long-established and readily pass legal muster. Other, more modern techniques may potentially not have had the time necessary for rigorous evaluation and scientific debate. Generally, cutting-edge techniques will be used more in the research laboratory setting. But, if contemplated for a forensic examination, then the Frye standard can become very important.
The Frye standard rose out of a 1923 legal decision (Frye v. United States ). The heart of the ruling was as follows: "Just when a scientific principle or discovery crosses the line between experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while the court will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs."
In the case of the ruling, the court found that an expert testimony to the jury on the use of a systolic blood pressure test at that time had not yet gained credibility in the scientific community, and so the evidence from the procedure was denied.
In modern times, the sophisticated molecular technologies that sequence deoxyribonucleic acid (DNA ) and determine the DNA profile of an individual can be held up to the legal scrutiny of the Frye standard. Typically, observance of defined and accepted protocols of sample collection, handling and analysis are sufficient to ensure the legal admissibility of the evidence.
The Frye standard also applies to the testimony of someone deemed to be an expert in a field that is relevant to the case (i.e., a ballistics expert). If the information is not presented in a convincing fashion (including citing scientific literature on the approach, use of the procedure, limitations of the procedure and general acceptance in the scientific community) or if the qualifications of the expert can be called into question, then the evidence can be ruled inadmissible.
As an example, in the 2004 Grady v. Frito-Lay trial in Pennsylvania, an associate professor of chemical engineering testified that the shape of the manufacturer's tortilla chip was a hazard, which could inflict injury to the mouth. The state Supreme Court used the Frye standard to rule that the expert's testimony was not generally accepted in the scientific community, and in fact represented inadmissible "junk science."
see also DNA; DNA profiling.