VII - Opinions and Expert Testimony

Opinions and expert testimony, general

·         Witness qualifications

o   competent

o   have personal knowledge

o   must take an oath or affirmation

·         Expert testimony on eyewitness reliability is allowed if it helps the jury understand potential perception or memory flaws, especially in cross-racial ID or trauma cases

Rule 701: Opinion Testimony by Lay Witnesses

·         To be admissible, testimony in the form of an opinion must

o   Be rationally based on the witness’s perception

o   Helpful to clearly understand the witness’s testimony

o   Not based on scientific, technical, or other specialized knowledge

·         Examples of generally allowed lay testimony

o   The identity of persons, things, and handwriting

o   Size, color, and weight of objects

o   Time and distance

o   Mental state or condition of another

o   Insanity and intoxication

o   Affection of one person for another

o   Physical condition of another, such as health or sickness

o   Values of property

·         The rule allows witnesses to make inferences based on what they see and express them in the form of an opinion

·         No clear line b/w facts, inferences, and opinions

·         The opinion cannot just relay something that the jury may easily reach

Rule 702: Testimony by Expert Witnesses

·         The Judge as “Gatekeeper”

o   They need to say

§  Expert is qualified

§  The expert is basing their opinion on reliable principles reliably applied

ú  Use Daubert factors

·         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:

o   their knowledge will help the trier of fact to understand the evidence or to determine a fact in issue

§  Testimony stating the obvious doesn’t satisfy this element

§  Conclusions by experts are not binding on the trier of fact

o   Be based on sufficient facts or data

o   Use reliable principles and methods, AND

o   Apply those reliable principles and methods to the facts

·         Use 403 to exclude evidence if probative value is outweighed by the prejudicial nature

·         Daubert v. Merrell Dow

o   Judges may consider these factors (non-exhaustive) when determining the reliability of expert testimony

§  Testability

§  Peer review

§  Error rate

§  Standards/controls

§  General acceptance in the relevant community (Frye)

·         Experts are not subject to the personal knowledge requirement

·         Polygraph results typically cannot be admitted because of questionable reliability and a high risk of prejudice

Rule 703: Bases of an Expert’s Opinion Testimony

·         Experts can base opinions on facts or data that the expert has (1) been personally aware of, or (2) personally observed

o   If experts in a particular field would reasonably rely on those kinds of facts or data in forming an opinion, they need not be admissible for the opinion to be admitted

o   But Inadmissible facts can be disclosed if their probative value substantially outweighs their prejudicial effect (reverse 803)

·         The expert may rely on facts of which she has personal knowledge, facts made known to her at trial, or facts known to her before entering the courtroom. 

·         If evidence is independently admissible, it may be used to (1) show the truth of the matter asserted AND (2) to evaluate the expert’s opinion. 

·         If evidence is admitted under Rule 703, it may only be used to evaluate the expert’s opinion.

704: Opinion on an Ultimate Issue

·         Experts may testify about ultimate issues in the case, but in criminal cases, cannot give opinions on whether the Δ possessed the required mental state or condition

705: Disclosing the Facts or Data Underlying an Expert Opinion

·         Experts may give opinions without first stating underlying facts; however, cross-examination can require disclosure

706: Court-Appointed Expert Witnesses

·         Courts can appoint neutral experts paid by the court

·         Both parties have the right to question and cross the expert

·         Parties can still call their own experts