FEDERAL RULES OF EVIDENCE
Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993), applied the rules governing expert testimony established by the Federal Rules of Evidence to the admission of scientific evidence at trials conducted in federal courts. Under the Federal Rules of Evidence, the trial judge acts as a gatekeeper, determining whether the proffered evidence is scientifically valid and relevant to the case at hand. Cross examination and the presentation of contrary evidence will allow the jury to determine whether the proffered scientific evidence is ultimately credible. With Daubert, the Court supplanted the old common-law test of Frye v. United States, which asked the courts to determine whether the scientific evidence was generally accepted in the relevant scientific community. Because each state is permitted to create unique rules of evidence for use in its courts, the Frye test, or some variation thereof, may still be used in those states which have not chosen to adopt Daubert.
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.
Rule 704. Opinion on Ultimate Issue
(a) Except as provided in subdivision (b), testimony in the form of an opinion or inference otherwise admissible is not objectionable because it embraces an ultimate issue to be decided by the trier of fact.
(b) No expert witness testifying with respect to the mental state or condition of a defendant in a criminal case may state an opinion or inference as to whether the defendant did or did not have the mental state or condition constituting an element of the crime charged or of a defense thereto. Such ultimate issues are matters for the trier of fact alone.
Rule 403. Exclusion of Relevant Evidence on Grounds of Prejudice, Confusion, or Waste of Time
Although relevant, evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.
CALIFORNIA RULES OF EVIDENCE
720.
(a) A person is qualified to testify as an expert if he has special knowledge, skill, experience, training, or education sufficient to qualify him as an expert on the subject to which his testimony relates. Against the objection of a party, such special knowledge, skill, experience, training, or education must be shown before the witness may testify as an expert.
(b) A witness' special knowledge, skill, experience, training, or education may be shown by any otherwise admissible evidence, including his own testimony.
721.
(a) Subject to subdivision (b), a witness testifying as an expert may be cross-examined to the same extent as any other witness and, in addition, may be fully cross-examined as to (1) his or her qualifications, (2) the subject to which his or her expert testimony relates, and (3) the matter upon which his or her opinion is based and the reasons for his or her opinion.
(b) If a witness testifying as an expert testifies in the form of an opinion, he or she may not be cross-examined in regard to the content or tenor of any scientific, technical, or professional text, treatise, journal, or similar publication unless any of the following occurs:
(1) The witness referred to, considered, or relied upon such publication in arriving at or forming his or her opinion.
(2) The publication has been admitted in evidence.
(3) The publication has been established as a reliable authority by the testimony or admission of the witness or by other expert testimony or by judicial notice. If admitted, relevant portions of the publication may be read into evidence but may not be received as exhibits.
722.
(a) The fact of the appointment of an expert witness by the court may be revealed to the trier of fact.
(b) The compensation and expenses paid or to be paid to an expert witness by the party calling him is a proper subject of inquiry by any adverse party as relevant to the credibility of the witness and the weight of his testimony.
CASE LAW
Kumho Tire Company v. Carmichael (97-1709) 526 US 137 (1999) 131 F.3rd 1433, reversed.
Ohio v. Sharma (CR 06-09-3248) 2007
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Is Fingerprint Identification Valid?
Rhetorics of Reliability in Fingerprint Proponents' Discourse
Cole, Simon A., Law & Policy, Vol. 28, No. 1 pp. January, 2006 pp.109-135
Abstract: Beginning around 1999, a growing number of scholars have claimed that validation studies for forensic fingerprint identification do not exist. This article revisits that claim by reviewing literature produced by proponents of fingerprint identification in response to that charge. It shows that fingerprint proponents employ rhetorical tricks in which they claim to address the validity question, but then subtly shift the question to ones that are easier to address. The article explores several different rhetorical strategies fingerprint proponents use to appear to be demonstrating validity, while in fact demonstrating other things. These include the fingerprint examiner's fallacy and the casework fallacy. The inability of fingerprint proponents to refute the charge that validity studies are lacking is further evidence that the charge is, in fact, correct.