Expert Witnesses Professor Caroline Cinquanto Professor Jeanine Linehan

Expert Witnesses Professor Caroline Cinquanto Professor Jeanine Linehan

§ Opinion Testimony by Lay Witnesses only if § (a) rationally based on witnesses perception; § (b) helpful to understand the witness’s testimony or determine a fact in issue; and § (c) not based on scientific, technical, or other specialized knowledge within the scope of Rule 702.

§ 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: § (a) helpful to the trier of fact; § (b) based on sufficient facts and data; § (c) reliable principles and methods; and § (d) apply principles and methods reliably.

An expert must have greater knowledge that a lay person. Once the expert is shown to have some expertise, the issue is then one of credibility. (e. g. carpenter, 1980 s hacker, recent med grad)

§ Used to be Frye – scientific tests and principles only admissible if those tests and principles have gained general acceptance in the particular field in which it belongs. § Now – Daubert – Key inquiry now is whether the evidence is relevant and reliable. Question: whether eh resonating or methodology underlying the testimony is scientifically valid and whether that reasoning or methodology can be applied to the facts in issue.

§ 1. Can it be tested? § 2. Subject to peer review? § 3. Known rate of error? § 4. Generally accepted? § Judge is the Gatekeeper and will hold a Daubert Hearing

§ Yes – impression testimony, cell tower evidence, DNA, fingerprint, breathalyzer § No – Cancer studies in mice and humans; tire failure analyst

Rule 703 states that an expert may base his opinion on facts and data not in evidence so long the facts and data are the type such experts reasonably use in their field. Furthermore, the facts and data need not be admissible for the opinion to be admitted. But if inadmissible, proponent can only disclose if the probative values outweighs the prejudicial impact. Opponent can always elicit facts (inadmissible or no) on cross. Why? To test the credibility of the opinion. § E. g. Expert based on lab reports, depositions and x-rays even if not admitted into evidence. §

§ An expert can testify without first testifying to the underlying facts or data. On cross, an expert can be required to disclose. § Why can this be helpful?

§ Opinion as to the Ultimate Issue § (a) In general: ok § (b) Exception: in a criminal case, cannot state if the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense.

§ Introduction § Name § Employment § Are you here today to render an opinion about XXXX? § Before we get to that opinion, I would like to talk about why your qualified to give that opinion.

§ Background § Education § Work History § Published § Awards § Honors

§ Your Honor, we tender the witness in the (area in which he is qualified – BE SPECIFIC) § Objection? § Voir Dire § Stipulate?

§ You stated earlier you were prepared to render an opinion about XXXXX. Before we get to that, please tell us what things you relied upon to come to your opinion. § Will your opinion be to a reasonable degree of XXXXX certainty? § Ask for the Opinion

§ Exhibits and visual aids § Role of the teacher § Simple language § Organized

Sample Voir Dire

Expert Opinion

§ Qualifications § Bias/Interest § Data Relied On § Assumptions § Prior Inconsistent Statements § Treatises § Experts Disagree