A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:See this Bernstein paper for an up-to-date discussion of how the federal rule is applied. This rule replaced the looser 1923 Frye rule about 15 years ago.
(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and methods; and
(d) the expert has reliably applied the principles and methods to the facts of the case.
California has stuck to the Frye rule, and calls it the Kelly-Frye rule after a 1976 California case called Kelly. Here is how the rule is codified:
801. If a witness is testifying as an expert, his testimony in the form of an opinion is limited to such an opinion as is:Now the California supreme court has moved a little closer to the federal standard in a Nov. 2012 case, Sargon v USC (.doc file).
(a) Related to a subject that is sufficiently beyond common experience that the opinion of an expert would assist the trier of fact; and
(b) Based on matter (including his special knowledge, skill, experience, training, and education) perceived by or personally known to the witness or made known to him at or before the hearing, whether or not admissible, that is of a type that reasonably may be relied upon by an expert in forming an opinion upon the subject to which his testimony relates, unless an expert is precluded by law from using such matter as a basis for his opinion.
We construe this to mean that the matter relied on must provide a reasonable basis for the particular opinion offered, and that an expert opinion based on speculation or conjecture is inadmissible. ...The way I read this, if an expert is testifying based on novel scientific techniques, then those techniques must have been published in the generally accepted scientific literature. Otherwise, the judge is supposed to follow this new "gatekeeper" re-interpretation of the California rule, and exclude unreliable testimony.
Thus, under Evidence Code sections 801, subdivision (b), and 802, the trial court acts as a gatekeeper to exclude expert opinion testimony that is (1) based on matter of a type on which an expert may not reasonably rely, (2) based on reasons unsupported by the material on which the expert relies, or (3) speculative. Other provisions of law, including decisional law, may also provide reasons for excluding expert opinion testimony.
[footnote] In People v. Leahy (1994) 8 Cal.4th 587, 604, this court held that the “general acceptance” test for admissibility of expert testimony based on new scientific techniques (see People v. Kelly (1976) 17 Cal.3d 24) still applies in California courts despite the United States Supreme Court’s rejection, in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579, of a similar test in federal courts. Nothing we say in this case affects our holding in Leahy regarding new scientific techniques.
If the California family court took its own rules of evidence seriously, then most of the child custody evaluations and other such expert testimony would be excluded as being unsupported and speculative. The child custody evaluators have never been able to show any reliability to their recommendations, and that should make their reports inadmissible. This Calif. supreme court case is a step in the right direction.
This is wishful thinking on my part, as I am sure that the family courts will ignore this decision. But in the long run, these quacks/experts will be seen as no better than astrologers.
Just look at the sloppy testimony that Arizona is allowing for Jodi Arias. I guess that the judge is bending over backwards so that the appeals court will agree that she got a fair trial and had every chance to make every argument. But the experts should have had to clearly explain what makes their testimony admissible. How do these experts have knowledge that is sufficiently beyond common experience? Where are they relying on generally accepted knowledge? How does that assist in the determination of facts?
About all I see is that Samuels could administer a multiple-choice computer-scored personality test, and read the DSM-IV symptoms for PTSD. LaViolette has no specific expertise, except maybe to say that a wide variety of behaviors can be reported as abuse. Everyone else is just unsupported opinion that is no better than astrology, and should not be admissible.
Yesterday, prosecutor Martinez more directly attacked the validity of the testimony of the domestic violence expert LaViolette, after making fun of her Snow White analysis and lecture. He asked if her opinion was subjective, and she seemed to not understand the question, and even argued that her testimony was as objective as any other testimony. Of course she was forced to admit that she was less objective than DNA expert testimony.
She then compared herself to an FBI profiler. This was a stupid analogy, because we would never convict someone from the word of an FBI profiler. He asked her if FBI profiler testimony is admitted in court, and she said that she did not know.
He went on to show that she made dozens of inferences about who was telling the truth, and he argued that these possibly-faulty inferences influence her conclusions.
She even said that her Continuum of Aggression and Abuse is used in California (730) child custody evaluations! Sigh.
I am not sure that the jury, or even the judge, understands this last point. The ideal expert witness would not make any factual inferences, and leave that to the jury. She might explain, for example, how PTSD or domestic violence is diagnosed and let jury decide whether the criteria are met. She might give recognized published data on how PTSD or DV relate to murder. She might even give condition testimony, such as saying that a particular conclusion is valid assuming that a story about an incident is true. But the jury gets to decide whether the jury is true.
LaViolette testified that Travis had a pattern of lying and that Jodi did not. Travis is dead. Jodi lied on national television, and proved that she can be a convincing liar.
Usually it is the responsibility of the judge, not the jury, to decide on the rules of evidence. But this case is out of control, and it will be up to the jury to make sense of it.
Update: (Tues, midday) The DV expert LaViolette continues to testify badly. She is quite evasive when asked about the possibility of secondary gain, ie, that Jodi was lying for the purpose of improving her legal situation. This is a crucial point, as the jury is making its own assessment of whether Jodi is telling the truth. LaViolette admits that lying is always possible, but refuses to explain how she finds Jodi credible. She only says that she did 44 hours of interviews, read a lot of documents, and formed an opinion.
A good expert witness would figure out a way to convey her expert knowledge about domestic violence, without injecting her personal opinion about Jodi's credibility. LaViolette has completely failed to do that.
With the jury outside the courtroom, LaViolette is confronted with the fact that Jodi's own parents told the police that Jodi has never been honest since she was 14 years old. Of course Jodi's parents' opinion is of dubious admissibility also, and has not been allowed.
The legal point here is that the judge has to drawn the line on hearsay evidence, or else the trial can break down to a lot of reputation trashing by outside parties. But this judge is allowing an expert to testify as just a way to sneak in a lot of inadmissible hearsay. The court needs to stick to the rules about expert testimony, in which case LaViolette would not be allowed.