Expert Testimony (702-705)
Question: Plaintiff in a toxic-spill case calls an environmental scientist who formed her opinion solely by reading an unpublished blog post summarizing foreign studies. Defense objects under Daubert.
Answer: Inadmissible — methodology is unreliable; reliance on untested secondary sources fails 702’s “reliable principles and methods” requirement.
Question: A lay witness testifies, “The defendant’s signature on this check looks forged to me.” Defense objects that only handwriting experts can say that.
Answer: Admissible — Rule 701 allows lay handwriting identification based on familiarity not acquired for litigation.
Question: Plaintiff seeks to authenticate an email allegedly written by Defendant using evidence that the writing style matches Defendant’s previous emails. Defense objects.
Answer: Admissible under Rule 901(b)(4) — distinctive characteristics, contents, and patterns may authenticate.
You may admit a hearsay statement if . . .
1. Declarant is unavailable,
2. Statement is so contrary to declarant's interest (PPP - Proprietary, Pecuniary, or Penal) that a reasonable person would not have said it unless it was true,
3. In criminal cases, if it tends to expose declarant to criminal liability and is offered to exculpate the defendant, you must also show corroborating circumstances indicating trustworthiness.
Question: Witness testifies, “When I asked the man why he ran, he said, ‘I thought the police were coming.’” Offered to show witness’s subsequent actions, not truth.
Answer: Not hearsay — offered for effect on listener, not for truth of statement.
Question: Defense expert in a homicide case testifies that Defendant’s brain-scan suggests “he lacks the neurological capacity for premeditation.” Prosecution objects.
Answer: Inadmissible under Rule 702 + 704(b) — improper opinion on whether Defendant had the required mental state.
Question: Bystander testifies, “It looked like the driver intended to run over the pedestrian.”
Answer: Inadmissible — lay opinion cannot infer subjective intent without perceptual foundation.
Question: A tweet is offered at trial. No witness saw Defendant post it, but metadata ties the tweet to Defendant’s phone, and the tweet mentions details only Defendant knew.
Answer: Admissible — sufficient circumstantial evidence under Rule 901(a).
Evan is charged with armed robbery. Evan offers testimony from his close friend, Carl, who says:
“Tony told me the night before he died, 'I robbed that liquor store alone. Jake had nothing to do with it.’”
Tony is unavailable because Tony is dead. There is no evidence tying Tony to the robbery. Will the court accept this statement?
Carl and Evan were close friends, giving Carl a reason to lie.
There is no physical evidence tying Tony to the robbery.
Result: Not admissible. No corroborating circumstances.
Question: Declarant testifies at trial and is subject to cross. Prosecution wants to introduce declarant’s prior unsworn statement made to police that is consistent with trial testimony but made after motive to fabricate arose.
Answer: Inadmissible under 801(d)(1)(B) — must precede the motive to fabricate.
Question: An accident reconstruction expert testifies but cannot explain the margin of error or the rate of error for his computer simulation. Opponent objects.
Answer: Likely inadmissible — Daubert requires known or potential error rates when using scientific or technical simulations.
Question: Store owner testifies that based on two decades of experience, “The damaged inventory is worth about $30,000 lost revenue.” Opponent argues this is expert testimony.
Answer: Admissible — owners may give lay opinions on value and lost revenue based on personal knowledge.
Question: Police seize a body-cam video. Officer who wore the camera does not recall the specific incident. Prosecution still seeks admission. Defense objects lack of foundation.
Answer: Admissible — video can be authenticated by showing it is what it claims to be even if the operator lacks specific memory.
Question: Witness refuses to testify despite being ordered to do so by the court. Prosecution declares witness “unavailable” and seeks to admit prior testimony.Under what circumstances may prosecution introduce prior testimony. May it be offered for it's truth?
Answer: Witness is unavailable under 804(a)(2); prior testimony admissible if opposing party had similar motive and opportunity to examine earlier. It may be offered for it's truth.
Question: Victim identifies Defendant in a lineup two hours after assault. At trial, victim forgets almost everything. Prosecution offers officer’s testimony that victim picked Defendant.
Answer: Admissible under 801(d)(1)(C) — prior identification; declarant must testify and be subject to cross even if memory fails.
Question: An expert economist bases expected-profit calculations on a hypothetical market scenario provided by Plaintiff’s counsel, not actual market data. Defense objects that assumptions are speculative.
Answer: Admissible if assumptions are supported by evidence; courts scrutinize but do not bar expert opinions solely because they rely on assumed facts (701–705 + case law).
Question: Witness says, “The argument sounded like it was about money.” Defense objects speculation.
Answer: Admissible — inference drawn from auditory perception is permitted if based on observed facts.
Question: A voicemail purportedly from Defendant is offered. Witness says the caller “sounded stressed, so it had to be him.”
Answer: Inadmissible — Rule 901(b)(5) requires familiarity with the voice, not emotional inference.
Question: Deceased declarant left a voicemail: “I drove over the line and caused the crash—my fault.” Offered in a civil case.
Answer: Admissible as statement against interest (804(b)(3)); penal/proprietary exposure + declarant unavailable.
Question: Witness denies making a prior statement; opponent introduces the statement but wants it admitted for truth under a hearsay exemption. Statement was unsworn.
Answer: Inadmissible for truth — 801(d)(1)(A) requires oath at prior proceeding; otherwise impeachment only.
Question: Expert testifies to an opinion but refuses to disclose proprietary formulas used in the analysis. Opponent objects under Rule 705.
Answer: Inadmissible — Rule 705 permits withholding underlying facts on direct, but not when expert refuses disclosure altogether; opposing party entitled to cross-examination of bases.
Question: Witness testifies, “The officer used excessive force.” Opponent objects.
Answer: Inadmissible — legal conclusions are not proper lay opinions under Rule 701.
Question: Bank produces duplicate microfilm records of transactions after originals were destroyed in routine scanning. Defendant objects authenticity.
Answer: Admissible — records created in the ordinary course and kept through reliable procedures satisfy 901(b)(1) and 902(11).
Question: A dying declarant says, “I don’t think I’ll make it—tell them the explosion happened because I ignored the safety rules.”
Answer: Admissible under dying declaration (804(b)(2)) if belief of imminent death shown and statement concerns cause/circumstances of impending death.
Question: Defendant’s friend testifies, “He told me, ‘I don’t trust banks, so I always keep cash at home.’” Offered to prove Defendant kept cash at home.
Answer: Inadmissible hearsay — statement not made by opposing party and does not qualify under any non-hearsay exemption; cannot be used to prove truth of matter asserted.