The Difference Between Expert and Lay Testimony of Witnesses

At common law, a witness could testify only to factual matters about which the witness had first-hand, personal knowledge.

The Colorado Rules of Evidence provide specifically for the admissibility of testimony in the form of opinions and inferences and separates such testimony into two categories: lay opinions and opinions by expert witnesses.

C.R.E. 701 of the Colorado Rules of Evidence (The Colorado Rules of Evidence) provides for the admissibility of testimony in the form of an opinion or inference of a witness not testifying as an expert. A witness may give testimony in the form of an opinion with respect to matters about which a person without specialized training would be competent to render a reliable judgment, provided the opinion is the kind of opinion that an ordinary person could make with reliability from observed facts.

For example, a witness may state an opinion regarding commonly observed matters, such as the speed of a vehicle

• a person’s state of sobriety,
• and the value of the witness’ property.
• a lay witness may also identify another person or thing

So long as the witness observed first-hand the physical facts upon which an opinion can be rationally based, the witness may state a lay opinion even if the witness cannot articulate all of the individual facts upon which the opinion rests.

Speculation, however, is not admissible. The opinion must be:

• helpful to a clear understanding of the witness’ testimony or the determination of a fact in issue. and
• rationally based on the witness’ own observations.

The sufficiency of evidence to establish the knowledge of a witness to express a lay opinion is a matter for the trial court to determine.

The weight to be given such opinions, if admitted, is for the jury to decide.

A lay witness is not prohibited from testifying to an issue of ultimate fact, provided the opinion is helpful and the questions eliciting the testimony are phrased to ask for a factual opinion, rather than a legal conclusion.

A witness qualified as an “expert”may state an opinion within the witness’ expertise. An expert opinion is admissible if:

1. the person testifying has knowledge, skill, training, education, or experience relevant to rendering the opinion; and
2. scientific, technical, or other specialized knowledge would assist the jury in understanding the evidence or a fact in issue.

The evidence upon which an expert opinion is based need not be admissible, provided it is reasonably relied upon by experts in that particular field. An expert cannot, however, base an opinion solely on the opinions of others.

An expert may state an opinion as to the ultimate issuesin the case. There is a distinction, however, between an opinion on an ultimate issue of fact and a “legal conclusion,” that is, whether a particular legal standard has or has not been met.

The trial courtdetermines whether a witness is qualified to render an expert opinion. The weight to be given the expert’s testimony is for the fact finder. The expert’s opinions are to be weighed and considered in the same manner as are those of other witnesses. In Colorado a trial judge has authority to appoint an expert witness to render an opinion.

In Colorado, the direct examiner is no longer required to first qualify and then formally tender the witness as an expert to the court for approval before the witness can give an opinion. Once the examiner establishes the witness’ expertise and qualifications, the examiner can proceed to elicit the relevant opinions without a formal imprimatur of the court. Opposing counsel may request voir dire in order to challenge the witness’ qualifications and the admissibility of the witness’ opinion and may cross-examine an expert witness concerning the basis of the expert’s opinion.

On some occasions it is advisable to request that the opposing party make an offer of proofoutside the jury’s presence as to the witness’ qualifications and testimony. This will enable counsel to clarify the witness’ field of expertise and the relevance of the proffered opinion and to conduct any voir dire challenges outside the presence of the jury. Then if any challenge to the witness is not sustained, the jury will not be left with any mis-impression that because the judge has overruled the challenge, the judge has determined that the witness’ expertise and opinions are unassailable.

An expert may be asked hypothetical questions. The form and admissibility of hypothetical questions is a matter within the trial court’s discretion. A hypothetical question need not include all facts shown by the evidence or pertinent to the ultimate issue, but should include only such facts as are supported by the evidence and should be in a form that will not mislead or confuse the jury. As previously stated, the expert may testify as to the “ultimate issue” in the case, although in the context of criminal trials, opinions as to guilt or innocence are deemed “not helpful” to the jurors and are therefore inadmissible.

On cross-examination, the examiner may use a “learned treatise” to test the witness’ knowledge. Counsel may read to the witness or have the witness read extracts from recognized authorities upon the subject matter and then ask the witness whether the witness agrees or disagrees with the authorities in order to compare the witness’ opinions with those stated in the treatise.

Expert testimony is being used with increasing frequency and in a broader range of areas in criminal trials as a result of the advent of new scientific techniques. The foundation for admissibility of expert scientific opinion is, however, a special category of expert testimony. When the expert’s testimony is based on novel scientific devices and processes involving manipulation or evaluation of physical evidence, the traditional Frye test is applied to determine admissibility.

Under the Frye standard, the admissibility of novel scientific evidence requires a showing that:

1. the underlying scientific theory or principle is generally accepted in the relevant scientific community; and
2. the techniques used to apply that theory or principle are generally accepted in the relevant scientific community.

The Frye test has been applied to expert testimony regarding polygraph examination results, voiceprint analysis, and experimental systems of blood typing. Admission of evidence which does not rely upon a novel scientific device or process is controlled by the more lenient standards of C.R.E. 702, not the restrictive Frye test.

Experts are routinely used to establish the identity of a substance as an illegal drug, the cause of death, the blood alcohol or drug content of blood, breath, and urine samples, the identity of a firearm to connect a particular weapon to the crime, or to establish the fact that a person recently did or did not fire a firearm .

Expert opinion testimony is also admissible to establish the identity of a perpetrator by using blood, semen, hair, saliva, toothmark, fiber, handwriting, and fingerprint comparisons. Experts have also testified as to blood-splatter patterns in order to reconstruct the course of events at the crime scene. Expert opinion is not admissible in Colorado on voice-print analysis.

There is a developing trend toward the use of experts to impeach or buttress the testimony of another witness. For example, experts may be called to give opinions on the reliability of eyewitness identification, and to testify about behavior that is consistent with being the victim of particular crimes, such as sexual assault. However, Colorado courts have consistently rejected expert testimony as to the truthfulness of a witness’ trial testimony.

An expert may render an opinion without prior disclosure of the underlying facts or data on which the opinion is based, unless the court requires otherwise. Crim.P. Rule 16, however, requires disclosure to the opposing party of the identity of any expert witness the party intends to call to testify at trial and the results of any tests conducted by the expert. Failure to disclose this information may preclude the use of the expert’s testimony at trial.

About The Author: H. Michael Steinberg Email The Author. A Denver Colorado Criminal Defense Lawyer or call his office at 303-627-7777 during business hours or call his cell if you cannot wait and need his immediate assistance 720-227-7777.

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