Daubert Standard
The Daubert standard is a rule of evidence regarding the admissibility of expert witness
Expert witness
An expert witness, professional witness or judicial expert is a witness, who by virtue of education, training, skill, or experience, is believed to have expertise and specialised knowledge in a particular subject beyond that of the average person, sufficient that others may officially and legally...

es' testimony
In law and in religion, testimony is a solemn attestation as to the truth of a matter. All testimonies should be well thought out and truthful. It was the custom in Ancient Rome for the men to place their right hand on a Bible when taking an oath...

 during United States federal legal proceedings. Pursuant to this standard, a party may raise a
, which is a special case of motion in limine
In limine
Motion in limine is a legal written "request" or motion to a judge which can be used for civil or criminal proceedings and at the State or Federal level. A frequent use is at a pre-trial hearing or during an actual trial requesting that the judge rule that certain testimony regarding evidence or...

 raised before or during trial
Trial (law)
In law, a trial is when parties to a dispute come together to present information in a tribunal, a formal setting with the authority to adjudicate claims or disputes. One form of tribunal is a court...

 to exclude the presentation of unqualified evidence
Evidence (law)
The law of evidence encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence can be considered by the trier of fact in reaching its decision and, sometimes, the weight that may be given to that evidence...

 to the jury
A jury is a sworn body of people convened to render an impartial verdict officially submitted to them by a court, or to set a penalty or judgment. Modern juries tend to be found in courts to ascertain the guilt, or lack thereof, in a crime. In Anglophone jurisdictions, the verdict may be guilty,...

. The Daubert trilogy refers to the three United States Supreme Court cases that articulated the Daubert standard:
  • Daubert v. Merrell Dow Pharmaceuticals
    Daubert v. Merrell Dow Pharmaceuticals
    Daubert v. Merrell Dow Pharmaceuticals, is a United States Supreme Court case determining the standard for admitting expert testimony in federal courts...

    , which held that Rule 702 of the Federal Rules of Evidence
    Federal Rules of Evidence
    The is a code of evidence law governing the admission of facts by which parties in the United States federal court system may prove their cases, both civil and criminal. The Rules were enacted in 1975, with subsequent amendments....

     did not incorporate the Frye "general acceptance" test as a basis for assessing the admissibility of scientific expert testimony;
  • General Electric Co. v. Joiner, which held that an abuse-of-discretion standard of review was the proper standard for appellate courts to use in reviewing a trial court's decision of whether expert testimony should be admitted;
  • Kumho Tire Co. v. Carmichael
    Kumho Tire Co. v. Carmichael
    Kumho Tire Co. v. Carmichael, , is a United States Supreme Court case that applied the Daubert standard to expert testimony from non-scientists.-Facts of the case:...

    , which held that the judge’s gatekeeping function identified in Daubert applies to all expert testimony, including that which is non-scientific.

Two of the most important appellate level opinions that clarify the standard include Judge Kozinski's opinion in Daubert on remand (
Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311 (9th Cir. 1995)), and Judge Becker's opinion in In re Paoli R.R. Yard PCB Litig., 35 F.3d 717 (3d Cir. 1994). Weisgram v Marley Co, 528 US 440 (2000) is also considered a significant case.


In Daubert, seven members of the Court agreed on the following guidelines for admitting scientific expert testimony:
  • Judge is gatekeeper: Under Rule 702, the task of "gatekeeping", or assuring that scientific expert testimony truly proceeds from "scientific knowledge", rests on the trial judge.
  • Relevance and reliability: This requires the trial judge to ensure that the expert's testimony is "relevant to the task at hand" and that it rests "on a reliable foundation". Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 584-587. Concerns about expert testimony cannot be simply referred to the jury as a question of weight. Furthermore, the admissibility of expert testimony is governed by Rule 104(a), not Rule 104(b); thus, the Judge must find it more likely than not that the expert's methods are reliable and reliably applied to the facts at hand.
  • Scientific knowledge = scientific method/methodology: A conclusion will qualify as scientific knowledge if the proponent can demonstrate that it is the product of sound "scientific methodology" derived from the scientific method
    Scientific method
    Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

  • Factors relevant: The Court defined "scientific methodology" as the process of formulating hypotheses and then conducting experiments to prove or falsify the hypothesis, and provided a nondispositive, nonexclusive, "flexible" test for establishing its "validity":
  1. Empirical testing: the theory or technique must be falsifiable, refutable, and testable.
  2. Subjected to peer review
    Peer review
    Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...

     and publication.
  3. Known or potential error rate.
  4. The existence and maintenance of standards and controls concerning its operation.
  5. Degree to which the theory and technique is generally accepted by a relevant scientific community.

In 2000, Rule 702 was amended in an attempt to codify and structure elements embodied in the "Daubert trilogy." The rule now reads as follows:
Rule 702. Testimony by Experts

If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.

(As amended Apr. 17, 2000, eff. Dec. 1, 2000.)


Although the Daubert standard is now the law in federal court and over half of the states, the Frye standard
Frye Standard
The Frye standard, Frye test, or general acceptance test is a test to determine the admissibility of scientific evidence. It provides that expert opinion based on a scientific technique is admissible only where the technique is generally accepted as reliable in the relevant scientific community. In...

 remains the law in jurisdictions including California, Florida, Illinois, New York, Pennsylvania, and Washington.

Although trial judges have always had the authority to exclude inappropriate testimony, previous to
Daubert, trial courts often preferred to let juries hear evidence proffered by both sides. Once certain evidence has been excluded by a Daubert motion because it fails to meet the relevancy and reliability standard, it will likely be challenged when introduced again in another trial. Even though a Daubert motion is not binding to other courts of law, if something was found not trustworthy, other judges may choose to follow that precedent. Of course, a decision by the Court of Appeals that a piece of evidence is inadmissible under Daubert would be binding on district courts within that court's jurisdiction.

Daubert motion: timing

To attack expert testimony as inadmissible, counsel may bring pretrial motions, including motions in limine. The motion in limine may be brought prior to trial, although counsel may bring the motion during trial as well.

A motion attacking expert testimony should be brought within a reasonable time after the close of discovery
Discovery (law)
In U.S.law, discovery is the pre-trial phase in a lawsuit in which each party, through the law of civil procedure, can obtain evidence from the opposing party by means of discovery devices including requests for answers to interrogatories, requests for production of documents, requests for...

 if the grounds for the objection can be reasonably anticipated. The hearing should be made well in advance of the first time a case appears on a trial calendar.

In one case where a Daubert hearing was conducted on the day of the trial, in which the district court excluded all plaintiff's expert testimony, resulting in the dismissal of all claims, the appellate court remanded the case because of multiple irregularities and a defective record of lower court proceedings.

The appellate court noted that in cases that rely heavily on expert testimony, a district court should set a discovery and trial schedule that realistically provides both sides with an adequate opportunity to introduce necessary evidence. The application of Federal Rule of Evidence 702 to proposed expert testimony can often be an uncertain process, and is best conducted in such a manner that litigants have a reasonable opportunity to locate experts who meet the rule's requirements.

In another case in which the defendant was apparently at fault for filing a motion to exclude expert testimony one week before the trial date, the district court denied the motion on that ground, but it advised the defendant that it might conduct its own voir dire
Voir dire
Voir dire is a phrase in law which comes from the Anglo-Norman language. In origin it refers to an oath to tell the truth , i.e., to say what is true, what is objectively accurate or subjectively honest, or both....

 of the expert in question before he testified. The district court preliminarily found that defendant's motion was predicated on a ruling made almost three months earlier by a district court in another state, and that defendant had shown no good cause for waiting to file the motion. The defendant ultimately lost that case, following the admission of the disputed expert testimony, and ultimately failed in its appeal.

An evidentiary hearing on the motion may not be necessary if the court finds that it would not assist the court in ruling on any of the matters in the motion.


Prior to Daubert, relevancy in combination with the Frye test were the dominant standards for determining the admissibility of scientific evidence in Federal courts. Frye is based on a 1923 Federal Court of appeals ruling involving the admissibility of polygraph
A polygraph measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions...

 evidence. Under
Frye, the Court based the admissibility of testimony regarding novel scientific evidence on whether it has "gained general acceptance in the particular field in which it belongs." The trial court's gatekeeper role in this respect is typically described as conservative, thus helping to keep pseudoscience
Pseudoscience is a claim, belief, or practice which is presented as scientific, but which does not adhere to a valid scientific method, lacks supporting evidence or plausibility, cannot be reliably tested, or otherwise lacks scientific status...

 out of the courtroom by deferring to those in the field.

Daubert, the Supreme Court ruled that the 1923 Frye test was superseded by the 1975 Federal Rules of Evidence
Federal Rules of Evidence
The is a code of evidence law governing the admission of facts by which parties in the United States federal court system may prove their cases, both civil and criminal. The Rules were enacted in 1975, with subsequent amendments....

, specifically Rule 702 governing expert testimony. Rule 702 originally stated (in its entirety),
"If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise."

In Daubert, the Court ruled that nothing in the Federal Rules of Evidence governing expert evidence "gives any indication that 'general acceptance' is a necessary precondition to the admissibility of scientific evidence. Moreover, such a rigid standard would be at odds with the Rules' liberal thrust and their general approach of relaxing the traditional barriers to 'opinion' testimony."


By requiring experts to provide relevant opinions grounded in reliable methodology, proponents of Daubert were satisfied that these standards would result in a fair and rational resolution of the scientific and technological issues which lie at the heart of product liability adjudication.

Ironically, Daubert has not appeared to further the Federal Rules philosophy of admitting generally all relevant testimony, and specifically of relaxing the traditional barriers to 'opinion' testimony." The
Daubert decision has instead been heralded by some political commentators as one of the most important Supreme Court decisions in imposing higher barriers for toxic tort
Toxic tort
A toxic tort is a special type of personal injury lawsuit in which the plaintiff claims that exposure to a chemical caused the plaintiff's injury or disease.-Different types:...

 and product liability
Product liability
Product liability is the area of law in which manufacturers, distributors, suppliers, retailers, and others who make products available to the public are held responsible for the injuries those products cause...

 cases, by allegedly reducing the volume of so-called junk science
Junk science
Junk science is a term used in U.S. political and legal disputes that brands an advocate's claims about scientific data, research, or analyses as spurious. The term may convey a pejorative connotation that the advocate is driven by political, ideological, financial, or other unscientific...

 in the court room.

According to a 2002 RAND
RAND Corporation is a nonprofit global policy think tank first formed to offer research and analysis to the United States armed forces by Douglas Aircraft Company. It is currently financed by the U.S. government and private endowment, corporations including the healthcare industry, universities...

 study, post Daubert, the percentage of expert testimony by scientists that was excluded from the courtroom significantly rose. This rise likely contributed to a doubling in successful motions for summary judgment in which 90% were against plaintiffs. Beyond this study, there is little empirical evidence of the impact of Daubert.
However, some critics argue that
Daubert has disrupted the balance between plaintiffs and defendants, “The exclusion of expert testimony affects plaintiffs far more than defendants because plaintiffs may then not be able to meet their required burden of proof. Furthermore, there is little point in plaintiffs going to the expense of Daubert motions to exclude defendant’s experts until they know if their case will proceed. So if more experts are now being excluded, then Daubert has undoubtedly shifted the balance between plaintiffs and defendants and made it more difficult for plaintiffs to litigate successfully.” Similarly, Daubert hearings can be subject to various abuses by attorneys attempting to bolster a weak case. These tactics can range from simply attempting to delay the case to driving up the costs of the litigation forcing settlement.

A different pattern has emerged in criminal cases. In criminal cases, the prosecution has the burden of proof and uses a host of forensic science methods as evidence to prove their case. But, Daubert motions are rarely made by criminal defendants and when they do, they lose a majority of the challenges. Some critics of the use of unreliable science in court argue that Daubert has had beneficial effects in civil litigation, but fails to address the underlying pathologies of the forensic science system that leads to dubious verdicts in criminal cases.

Some commentators believe that
Daubert caused judges to become—in the phrase used in former Chief Justice William Rehnquist
William Rehnquist
William Hubbs Rehnquist was an American lawyer, jurist, and political figure who served as an Associate Justice on the Supreme Court of the United States and later as the 16th Chief Justice of the United States...

’s dissent in
Daubert—amateur scientists, many lacking the scientific literacy
Scientific literacy
Scientific literacy encompasses written, numerical, and digital literacy as they pertain to understanding science, its methodology, observations, and theories.-Definition:...

 to effectively fulfill their role as gatekeeper of scientific evidence. Although “science for judges” forums have emerged in the wake of
Daubert in order to educate judges in a variety of scientific fields, many are still skeptical about the usefulness of the Daubert standard in discerning valid science. The responsibility to assess scientific relevance has shifted from highly-trained expert witnesses to judges deficient in science education. The "Daubert" ruling furthermore admits the possible introduction of non-peer reviewed data and conclusions. This increasingly shifts the burden of scientific judgement onto judges who have not had an education which would enable them to properly evaluate such data.

Pursuant to Rule 104(a), in Daubert the U.S. Supreme Court suggested that the following factors be considered:
  1. Has the technique been tested in actual field conditions (and not just in a laboratory)? [e.g. fingerprinting has been extensively tested and verified not only in laboratory conditions, but even in actual criminal cases. So it is admissible. Polygraphy on the other hand has been well tested in laboratories but not so well tested in field conditions]
  2. Has the technique been subject to peer review and publication?
  3. What is the known or potential rate of error?
  4. Do standards exist for the control of the technique's operation? [e.g. the use of penile plethysmography for sex offender risk assessment is being used by different workers according to their own standards. Thus penile plethysmography does not meet Daubert criteria]
  5. Has the technique been generally accepted within the relevant scientific community? [this test was earlier the only relevant criterion under Frye]

The Supreme Court explicitly cautioned that the Daubert list should not be regarded by judges as “a definitive
checklist or test...” Yet in practice, judges have judged the admissibility of scientific evidence using the "Daubert factors" as a checklist; for example, the trial court judge in
Kumho admitted to erroneously treating the factors as mandatory.

International influence

In 2005, the United Kingdom House of Commons Science and Technology Committee recommended the creation of a Forensic Science Advisory Council to regulate forensic evidence in the UK and observed that:
The Law Commission for England and Wales has proposed a consultation paper (No.190) to adopt a criterion like the Daubert Standard to help reform the law of evidence in regards to the admissibility of scientific evidence.

External links

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