Lay Opinion
When is lay opinion admissible under FRE 701?
When it is rationally based on the witness’s perception, helpful to the jury, and not based on specialized knowledge.
Can a police officer testify about the meaning of coded drug jargon based on training?
Yes, but only as expert testimony under FRE 702, not as lay opinion.
What must an expert show to be qualified under FRE 702?
Knowledge, skill, experience, training, or education sufficient to assist the jury.
Under FRE 703, may an expert rely on inadmissible hearsay?
Yes, if experts in that field reasonably rely on that type of information.
A homeowner testifies that mold in the basement “caused my respiratory illness.” Admissible?
No. Determining medical causation requires expert testimony.
May a lay witness testify that someone “seemed drunk”?
Yes. Recognizing intoxication from personal observation is within common experience.
Can a business owner give lay opinion about the value of their business?
Yes, if based on personal knowledge and experience operating the business.
What is the judge’s role under Daubert?
The judge must evaluate reliability of the methodology and its application. Basically, the judge acts as a gatekeeper who must decide whether expert testimony is reliable enough to be heard by the jury. This doesn't mean the judge decides whether the expert is right, just whether they are using reliable methodology applied reliably to the case. Remember, Judge gets the power and responsibility to make this determination from 104(a).
May inadmissible underlying data relied on by an expert be disclosed to the jury?
Only if the probative value substantially outweighs the risk of unfair prejudice.
An eyewitness testifies that two gunshots sounded “closely spaced together.” Admissible?
Yes. Describing sounds based on perception is permissible lay opinion.
May a lay witness estimate the speed of a moving vehicle?
Yes. Speed estimation based on perception is permitted as lay opinion.
May a lay witness interpret medical records or explain causation?
No. That requires scientific or technical expertise.
Are clinical experience and professional judgment sufficient for expertise even without formal scientific testing?
Yes, if the reasoning process is reliably applied.
Under FRE 704(a), can an expert give an opinion on an ultimate issue?
Yes, unless it states a legal conclusion. For example, in a DUI case an expert testifies that basedon on blood test and their analysis, D's bac was .19 at the time of driving. This i sokay because it does not tell the jury how to apply the law, it describes a scientific fact.
A mechanic testifies, without being qualified as an expert, that brake failure occurred due to “hydraulic pressure loss.” Admissible?
No. That requires specialized mechanical expertise.
May a lay witness identify an emotion (e.g., “he looked scared”)?
Yes, if based on observed demeanor and helpful to the jury.
May a lay witness familiar with the defendant identify them on surveillance video?
Yes, if familiarity makes the identification more helpful than the jury’s own observation.
May an expert testify using a methodology that lacks peer review but is widely used in the field?
Possibly yes, if the method is reliably applied and accepted within the field. Expert testimony is reliable when (1) the methodology rests on a reliable foundation and (2) the expert has reliably applied that methodology to the facts, assessed under the flexible Daubert/Kumho factors. (testability, peer review, known error rate, general acceptance, etc.)
Under FRE 704(b), what is forbidden?
In a criminal case, an expert cannot opine on whether the defendant had the required mental state.
A forensic accountant uses spreadsheets prepared by assistants. May they rely on them?
Yes. Experts may rely on data prepared by others if such reliance is customary in the field.
May a lay witness opine that a pattern of behavior is consistent with “grooming” in a sexual abuse case?
No. That requires specialized knowledge and thus expert testimony.
May a computer programmer testify as a lay witness that code “appears malicious”?
No. Determining malicious coding requires specialized knowledge and is expert testimony.
Can a court exclude expert testimony because the expert leaps from data to conclusion without explaining the reasoning?
Yes. Unsupported assertions are inadmissible under FRE 702.
May an expert testify that the defendant did not “intend to kill”?
No. That violates FRE 704(b).
A gang expert testifies that a defendant’s social media post uses a symbol indicating intent to commit a hit. Admissible?
Yes, if the expert is properly qualified and the testimony is based on reliable knowledge of gang symbolism.