Expert Testimony
Question: Prosecution calls a chemist who identifies white powder as cocaine using a testing method not generally used in the field and unsupported by peer review. Defense objects under Daubert.
Answer: Inadmissible — Rule 702 requires reliable principles and methods; lack of general acceptance, peer review, and known error rate undermines reliability under Daubert.
Question: A lay witness testifies, “Based on how he was slurring and stumbling, he was definitely drunk.” Defense objects that this is an expert conclusion.
Answer: Admissible — Rule 701 permits lay opinions rationally based on perception and helpful to the jury; intoxication is a classic lay-opinion subject.
Question: Prosecution seeks to admit a threatening text message from a phone allegedly belonging to Defendant. Evidence: SIM card registered to Defendant, nickname references in text, timing matched surveillance. Defense objects lack of authentication.
Answer: Admissible under Rule 901(a) — circumstantial evidence supporting a finding that Defendant authored the message.
Question: Prosecutor seeks to introduce graphic autopsy photographs. Defense argues their probative value is minimal because manner of death is undisputed.
Answer: Likely inadmissible — under Rule 403, unfair prejudice substantially outweighs limited probative value when facts shown are undisputed.
Question: Prosecutor offers a gun found in Defendant’s home to prove it was the murder weapon. No forensic match has yet been shown, but prosecutor plans to call ballistics next. Defense objects relevance.
Answer: Conditionally admissible under Rule 104(b) — relevance depends on later proof; judge admits subject to connecting evidence.
Question: An expert accident reconstructionist forms an opinion entirely based on conversations with eyewitnesses and police reports. Defense objects hearsay. Prosecution asks to disclose the hearsay to the jury.
Answer: Under Rule 703, expert may rely on inadmissible hearsay if reasonably relied upon, but hearsay may be disclosed only if its probative value substantially outweighs prejudice.
Question: A lay witness says, “It looked like the defendant was planning a robbery.” Prosecution argues it's permissible. Defense objects speculation.
Answer: Inadmissible — Rule 701 prohibits lay opinions not based on perception and that infer unobserved mental states or intent.
Question: Party offers a copy of a photograph downloaded from social media. Opponent objects the photo could have been altered.
Answer: Authentication requires only a prima facie showing; testimony that the image fairly and accurately depicts what it purports to show satisfies Rule 901.
Question: Defendant wants to introduce victim’s past conviction for burglary to show victim was “the type to start fights.” State objects.
Answer: Inadmissible — extremely high unfair prejudice and impermissible character use outweighs minimal probative value under 403.
Question: Plaintiff introduces shoe prints from crime scene, asserting they match Defendant’s boots. No expert has yet testified to similarity. Defense objects.
Answer: Conditionally admissible — relevance depends on showing a connection; if later evidence fails, the court may strike.
Question: Defense calls a psychiatrist to testify that “the defendant lacked the specific intent to commit robbery.” Prosecutor objects under Rule 704(b).
Answer: Inadmissible — Rule 704(b) bars experts in criminal cases from opining directly on whether defendant had the required mental state.
Question: A business owner testifies to the value of her own equipment without being qualified as an expert. Opponent objects.
Answer: Admissible — Owners may give lay opinions about value if based on personal knowledge (Rule 701).
Question: Police introduce surveillance footage. Defense argues someone must testify who actually installed the camera.
Answer: Not required — Rule 901 permits authentication through any witness with knowledge that the video accurately represents the scene.
Question: In a drug-trafficking trial, prosecution offers photos of Defendant posing with guns and money two years prior. Defendant had no weapons in current case.
Answer: Likely inadmissible — weak relevance and strong prejudice; background lifestyle evidence is excluded under 403 when not tied to charged conduct.
Question: Prosecutor offers evidence Defendant fled the scene to show consciousness of guilt. Defense argues there is no proof Defendant knew he was a suspect.
Answer: Admissible under 104(b) — conditional relevance; jury decides whether flight indicates guilt once minimal evidence supports inference.
Question: Plaintiff calls an engineer as an expert. Engineer testifies he has “no formal training,” but built expertise through 25 years of field experience installing identical machines. Defense argues he is unqualified.
Answer: Admissible — Rule 702 allows qualification by knowledge, skill, experience, training, or education; extensive field experience suffices.
Question: Witness says, “From what I observed, the car was going at least 70 mph.” Defense objects that speed estimation requires expert analysis.
Answer: Admissible — lay witnesses may estimate speed when based on personal perception.
Question: A witness identifies Defendant’s voice from a recorded call based on a single prior encounter six months earlier. Defense objects.
Answer: Admissible — Rule 901(b)(5) allows voice identification by anyone familiar with the voice under circumstances connecting it to the declarant.
Question: Prosecutor introduces defendant’s gang tattoos to show identity because eyewitness described similar tattoos. Defendant argues 403.
Answer: Admissible — tattoos directly link to identity; probative value outweighs prejudice under Rule 403.
Question: Plaintiff attempts to introduce evidence Defendant threatened a third party “days before the accident” to show Defendant’s aggressive disposition. Defense objects relevance.
Answer: Inadmissible — conditional relevance requires a logical link; threat to unrelated third party does not make any material fact more or less probable.
Question: An expert testifies on direct examination to all opinions but withholds underlying facts. On cross, defense demands disclosure of those underlying facts. Prosecution objects.
Answer: Under Rule 705, experts may state opinions without first testifying to underlying facts, but cross-examination allows full inquiry into those bases.
Question: Witness claims, “Based on his demeanor, the defendant was lying.”
Answer: Inadmissible — Rule 701 bars lay witnesses from offering credibility opinions about another witness or party.
Question: Prosecution seeks to authenticate a handwritten note; handwriting expert testifies based on samples prepared by Defendant after charges were filed. Defense objects.
Answer: Inadmissible — Rule 901(b)(3) prohibits handwriting comparisons using exemplars prepared for litigation unless proven reliable; risk of manipulation.
Question: Defense offers evidence that Plaintiff once falsely accused someone else of a crime years earlier. Plaintiff objects Rule 403.
Answer: Admissible — probative of bias, motive, or credibility; prejudice does not substantially outweigh probative value.
Question: Prosecution offers evidence Defendant purchased chemicals used in bomb-making. Defense argues irrelevance. Prosecution claims it will show Defendant also possessed detonators and plans.
Answer: Conditionally admissible under Rule 104(b) — relevance depends on later evidence tying chemicals to charged conduct.