Quite often, expert opinions can verge on the outlandish. I’m sure there’s some reason to have expert testimony on UFO abductions, ESP and spirit channeling for some particular court cases. In my experience, the expert testimony is not so fanciful, but there will be attempt to dress up the expert’s purchased "junk science" opinion as based on some science, when in fact, it doens't qulaify as science.
A quick review of how state courts handle expert opinion testimony is in order. In most cases, a witness can only testify on matters within the witness’s personal knowledge. Evidence Code § 702. Generally, a witness can only testify as a “percipient” witness. “Perceive” means to acquire knowledge through the senses. Evidence Code § 170. Such witnesses testify only about facts, not opinions, in court. There are some matters in which such witnesses can express opinions, but those are limited. Evidence Code §800. Evidence Code § 813 permits a property owner to offer an opinion on the property’s value, for example. And if you are an “intimate acquaintance of a person, you my render an opinion as to that person’s sanity without any medical qualifications. (This bit of legal trivia comes in handy at cocktail parties!) Evidence Code § 870. Also, if you are familiar with the handwriting of another you can express an opinion on whether a document is in that person’s handwriting. Evidence Code § 1416. (I’ll leave aside the sometimes difficult question of distinguishing between “facts” and “opinions.”)
Nevertheless, the general rule is that only experts can provide opinion testimony at trial. Opinions are limited to those sufficiently outside common experience that they would be useful to the trier of fact. They must also be based on the expert’s qualifications, including special knowledge, skill, experience and training. Quite often the expert’s opinions will sound scientific but will not be. It will be up to the attorney to prevent unqualified “junk science” from coming into evidence.
There are two sections of the evidence code that provide for this procedure. First, Evidence Code § 802 permits an expert to be examined on the basis for the opinions by the opposing party before being permitted to express the opinions. The preliminary facts, such as the qualifications of the expert and whether the opinion will help the trier of fact at all, or is merely “junk science,” can be determined by the court outside the presence of the jury in a hearing conducted under Evidence Code § 402. Often this issue is raised in a pretrial motion in limine.
Challenging junk science opinions should begin by defining “science” to the court. Here, the Federal Judicial Center has been particularly helpful by publishing its “Reference Manual On Scientific Evidence.” As this is from a neutral and scholarly source heavily relied upon by federal judges, it should be persuasive to state judges as well. This document is lengthy but should be reviewed before the deposition of any dubious experts in a particular case so that the questions relating to the science can track the manual and provide later support for the motion in limine, or questioning at a 402 hearing or at voir dire at trial. There is no question that a lot of junk science testimony gets into the courtroom becasue it is not challenged by the opposing side. This Manual provides the general informaiton needed to challenge a "junk science" expert.
It is important that the expert you have hired understands the legal rules regarding experts and the necessity to be able to back up the opinions expressed. If you are faced with an opposing expert who is professing some form of junk science, then the Reference Manual should be reviewed prior to that expert’s deposition so that the answers to deposition questions can be used as a basis to exclude the expert’s junk science opinions on a motion in limine, at a 402 hearing or during trial when the expert can be cross examined on voir dire.
I will analyze California’s legal standard regarding admissibility of expert testimony and compare it with the federal standard in a later article.
Comments