Editing Expert witness (section)

===Scientific evidence===

In [[law]], '''scientific evidence''' is evidence derived from [[Science|scientific]] knowledge or techniques. Most [[Forensics|forensic evidence]], including [[DNA profiling|genetic evidence]], is scientific evidence.<ref>{{cite journal |last1=Stern |first1=Hal S. |last2=Cuellar |first2=Maria |last3=Kaye |first3=David |title=Reliability and validity of forensic science evidence |journal=Significance |date=April 2019 |volume=16 |issue=2 |pages=21–24 |doi=10.1111/j.1740-9713.2019.01250.x|s2cid=159219970 |doi-access=free }}</ref><ref>{{cite journal |last1=Giannelli |first1=Paul C. |last2=McMunigal |first2=Kevin C. |title=Prosecutors, Ethics, and Expert Witnesses |journal=Fordham Law Review |date=2007 |page=1509}}</ref>

==== ''Frye'' test ====
The ''Frye'' test, coming from the case ''[[Frye v. United States]]'' (1923), said that admissible scientific evidence must be a result of a theory that had "general acceptance" in the scientific community. This test results in uniform decisions regarding admissibility. In particular, the judges in ''Frye'' ruled that:

: ''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 courts 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.''<ref>Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).</ref>

In 1923, the case of Frye v. United States instituted significant change to both criminal and civil law by addressing the use of expert witness testimony in conjunction with scientific testimony. In Frye v. United States, the defense team attempted to introduce both the results of a polygraph test administered to Frye to determine Frye's innocence as well as the testimony of an expert witness to verify and explain the results.

However, the court rejected the expert's testimony, ruling that: "While courts 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."<ref name=":0" />

Through this ruling, the judge's opinion in Frye v. United States set precedent and the standard by which expert witnesses would be utilized in the court system for decades. In the federal courts, between 1948 and 1975, Frye was cited 55 times; however, the use and application was not consistent.<ref name=":0" /> One of the major struggles that came out of this precedent was the application to both civil and criminal cases. Many of the courts and judges had trouble interpreting the "general acceptance" notion of a particular field in a concise and non-arbitrary manner. In 2012, courts in nine states still used the ''Frye'' standard when analyzing state expert witness rules.<ref name=":3">{{Cite book|last=Fisher|first=George|url=https://www.worldcat.org/oclc/823514237|title=Evidence|year=2013|isbn=978-1-60930-060-9|edition=3|location=New York|pages=807–10|oclc=823514237}}</ref>

'''The Federal Rules of Evidence'''

In 1975, the United States Congress issued the Federal Rules of Evidence. FRE 702 was issued to provide a standard for expert witness testimony to be upheld by the United States court system. The rule specified that the application of expert witnesses had to be attributed to a person with "scientific or technical knowledge," in conjunction with a list of qualifications that would quality one to be an expert in terms of "knowledge, skill, experience, training or education".<ref name=":2" /> This rule thus clarified the acceptable use of expert witnesses in both criminal and civil cases.

However, FRE 702 still left some courts in confusion. The courts who would use this new rule were confused as to whether FRE 702 served to bolster the "general acceptance" ruling in Frye or if FRE 702 was the replacement of this rule. For instance, in ''U.S. v. Williams'' (1978), the [[United States Court of Appeals for the Second Circuit|Second Circuit]] responded that "the applicable considerations [for expert witness testimony] are 'probativeness, materiality, and reliability of the evidence on the one side, and any tendency to mislead, prejudice or confuse the jury on the other.'"<ref name=":2" /> The court appeared to reject the previous precedent set by ''Frye''.<ref name=":4">{{Cite web|last1=Ryskamp|first1=Dani Alexis|last2=J.D.|date=2018-05-10|title=A Brief History of Expert Witnesses in U.S. Courts|url=https://www.expertinstitute.com/resources/insights/a-brief-history-of-expert-witnesses-in-u-s-courts/|access-date=2021-11-01|website=Expert Institute|language=en-US}}</ref> The rationale in the Williams case was later adopted by other federal courts, including the [[United States Court of Appeals for the Third Circuit|Third Circuit]] which adopted a "reliability" test in 1984.<ref name=":4" /> Meanwhile, other federal courts stuck to the ''Frye'' precedent, causing a [[circuit split]] which would not be solved until the Supreme Court set a new expert standard in [[Daubert v. Merrell Dow Pharmaceuticals, Inc.|''Daubert v. Merrell Dow Pharmaceuticals, Inc.'' (1993)]].<ref name=":4" />

==== Daubert standard ====
The [[Daubert standard]] arose out of the U.S. Supreme Court case ''Daubert v. Merrell Dow Pharmaceuticals, Inc.'' It provides four factors that courts ought to consider when determining whether expert testimony is admissible under the Federal Rules of Evidence:<ref name=":4" /><ref>Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993).</ref>

#"Whether the expert's theory or technique can be (and has been) tested"
#"Whether the theory or technique has an acceptable known or potential rate of error"
#"The existence and maintenance of standards controlling the technique's operation"
#"Whether the theory or technique has attained 'general acceptance'"

In 2012, twenty-two states used the ''Daubert'' test when analyzing their own expert witness rules.<ref name=":3" />