Evidence - Lay and Expert Opinions

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Lay and Expert Opinions


General rule of personal knowledge and three general exceptions

Rule 602 generally requires witnesses to have personal knowledge of the matters they testify to.

1. Lay opinions (Rule 701)
2. Expert opinions (Rules 702-705)
3. Out-of-court admissions of party opponents (Rule 801?)

Standard for admission of lay opinions (3 requirements) [Rule 701]

Lay opinion testimony must be:
1. Rationally based on the witness's perception;
2. Helpful to clearly understanding the witness's testimony or to determining a fact in issue; and
3. Not based on scientific, technical, or other specialized knowledge within the scope of Rule 702 (expert).

Lay opinions - "collective facts" doctrine

A "collective fact" is really a shorthand rendition of what the witness perceived. The event observed may involve so many details that what registers in the witness's mind is an overall impression more than specifics. That impression must be the sort of inference that laypersons commonly and reasonably draw. If expert testimony is instead needed to support the inference, the layperson may not draw it.

E.g. a witness's opinion that ∆ acted drunk might be more helpful than describing all the minute details that demonstrated intoxication, and is probably the type of inference that a layperson may reasonably draw.

Lay opinions - skilled lay observer opinion

Skilled lay observer opinion lies between lay and expert testimony. Such opinions are offered when a layperson has prior experience that enables laypersons with such experience reasonably to draw the proffered conclusion. The skilled lay observer cannot be testifying about something scientific or technical, but must have experience or information not common to all laypersons but falling short of the "specialized knowledge" required of experts.

Policy - Why are expert opinions needed?

In many cases, where generalizations are beyond everyday experience, a full, fair, and informed jury decision requires expert guidance to understand the facts. A dispute may involve info beyond the knowledge or capabilities of a typical juror, so parties are allowed to present testimony by expert witnesses.

But, because of the undue weight that jurors are likely give to exert testimony, rules are needed to limit the misuse of such evidence. Jurors are more likely to be "overawed" and accept the expert's opinions as truth, instead of using their own powers of deduction.

Five important issues connected with expert testimony

1. What topics are appropriate for this type of testimony [a subject is appropriate for expert testimony if an expert's opinion on it would assist the trier of fact]
2. Who should be permitted to testify as an expert [a person can qualify as an expert witness by a showing of knowledge or experience]
3. Probable reliability of the testimony [reliable principles and methods must be applied to the facts of the case]
4. What types of data an expert may rely on to form an opinion [an expert's opinion can be based on any data that experts in the field ordinarily use, but it must apply reliable principles to sufficient data related to the case]
5. Whether the style or form of the testimony should be restricted [an expert may state an opinion or conclusion based on the facts the expert believes to be true or may answer a hypothetical question that asks the expert to make assumptions]

Five requirements for expert opinion to be admissible [Rule 702]

1. expert is qualified by knowledge, skill, experience, training, or education;
2. Expert's scientific, technical, or other specialized knowledge will be helpful to understanding the evidence or determine a fact in issue;
3. The testimony is based on reliable data ("based on sufficient facts or data" and "the product of reliable principles and methods")
5. The testimony fits the facts of the case ("the expert has reliably applied the principles and methods to the facts")

Four potential data sources for expert witnesses [Rule 703]

1. Firsthand observations made by expert out of court
2. Information provided to expert in the courtroom that expert is asked to assume is accurate
3. Expert's observation of in-court testimony by witnesses
4. Facts or data made known to expert out of court

Does the basis for an expert's opinion need to be admissible? [Rule 703]

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

But if the facts or data would otherwise be inadmissible, the proponent of the opinion may disclose them to the jury only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.

Disclosing the facts or data underlying an expert's opinion [Rule 705]

Unless the court orders otherwise, an expert may state an opinion — and give the reasons for it — without first testifying to the underlying facts or data. But the expert may be required to disclose those facts or data on cross-examination.

The "ultimate issue" rule for expert testimony [Rule 704]

An opinion is not objectionable just because it embraces an ultimate issue.

However, in a criminal case, an expert witness must not state an opinion about whether the defendant had a mental state that constitutes an element of the crime or a defense.

Rules 701 and 702 still require that opinions be helpful to the trier of fact, and it could still be excluded under Rule 403.

The "opinion rule" for hearsay and lay/expert opinions

If a hearsay document is admitted and contains opinions, including expert ones, many courts would only admit the opinion if it complies with the opinion rules, like Rule 701 through 705, that would apply were a live witness to state the opinion on the stand. [doesn't apply to statements admitted as party admissions]

The "learned treatise" doctrine for attacking expert opinions [Rule 803(18)]

A common way of attacking an expert's credibility is by revealing contradictions between the expert's assertions and those made by other experts in published works, provided:

1. Contained in a treatise, periodical, or pamphlet
2. The statement is called to the attention of an expert witness on cross or relied on by the expert on direct.
3. The publication is established as a reliable authority by the expert's, by another expert, or by judicial notice

Statements from learned treatises may be read into evidence but not received as an exhibit.

Eleven common ways of attacking an expert's credibility [probably not very important for exam]

1. Exploring how the non-existence of any particular basis on which the expert relied would alter his or her opinion
2. Exploring how the existence of contrary or additional bases
would alter the expert's opinion
3. Determining which materials the expert reviewed or failed to review in preparing to offer the opinion
4. Determining which testes or other investigations the expert conducted (or failed to conduct) and how they were done
5. Exploring the financial compensation received
6. Revealing contradictions between the expert's assertions and those made by other experts in published works
7. Exploring what prior expert testimony the expert has given
8. Posing a hypothetical question based upon an alternative set of assumptions
9. Challenge the assumptions of witnesses truthfulness
10. If expert relied only on certain pieces of evidence to form his opinion, point that out
11. Tests or investigations the experts did; different methods that could have been used

Scientific evidence - The Frye Test

The thing (method/principle) from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs. Must be valid, reliable, accurate, and yield consistent results.

The problem was that this resulted in excluding new techniques that aren't generally accepted yet.

Scientific evidence - Daubert (not on the exam)

The Daubert court stressed that the standard should be "relevancy and reliability," and provided a non-exaustive list of factors:

1. Is the theory (underlying principle) and the technique applying that theory (method) testable and have they been tested?
2. Have the theory and technique been subjected to peer review and publication?
3. What is the known or potential error rate of the technique?
4. Are there standards controlling the technique's operation, that is, an authoritative statement of the circumstances under which the technique's application to a particular case will be considered trustworthy?
5. Has the principle or technique attained "widespread acceptance"? (The Frye Test)

Scientific evidence - Kumho Tire

All expert testimony, including "technical and other specialized knowledge," is governed by Daubert's "relevancy and reliability" standard.

Can the court appoint expert witnesses?

Yes - see Rule 706

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