When Daubert came out, it did away with the Frye standard. And it—for the first time—put in a gatekeeping responsibility for judges.
Judges play a crucial role as the gatekeeper for scientific testimony in the courtroom. They may decide to prohibit testimony on certain pieces of evidence for any number of reasons. More likely than not the judge will allow the evidence into the court, though they then must decide if any limitations are required to ensure that the fact-finders have the best possible chance for applying the proper amount of weight to the evidence.
The judicial system allows for introduction of scientific evidence, as long as it will assist and not unduly prejudice the trier of fact. An expert opinion is usually provided to present the evidence. The expert’s testimony can reflect:
Whether or not experts are allowed to testify on their specialized opinions is up to the judge. In general, an expert must be “qualified” as such every time s/he goes into a courtroom to give an opinion.
A judge assesses admissibility of scientific evidence (or testimony) by determining if the techniques or theories applied are scientifically sound, and were derived from scientifically rigorous examination. This may include assessing the following:
Once the assessment of the general theory is made, the gatekeeping function continues by ensuring that there were sufficient facts and data to be applied, and that the theory or technique was properly applied to those facts/data.
In addition, if the evidence is found to be scientifically valid, the judge must consider whether the evidence will have the tendency to assist the trier of fact. In doing so, the judge may also consider whether the evidence is confusing or unfairly prejudicial to a degree that outweighs its probativeness.
Finally, this analysis is not supposed to focus on the expert’s conclusions, but only on the reliability of the methodology. As the Court wrote in Daubert, “The focus, of course, must be solely on principles and methodology, not on the conclusions that they generate.” However, it must be shown that the conclusion can reasonably follow from sufficient data and a proper methodology.
More often than not, testimony /evidence will be admitted into the courtroom. Once admitted, it is up to the parties to ask questions about the evidence or testimony that are likely to draw out factors that could show the evidence as more or less reliable/valid.
For a deeper understand of admissibility and weighing evidence, view Error Rates, Academic Validity and other media links on the right side of this page, and visit the Weighing the Evidence section.