Plain-English summary
Court rules experts may testify that 'most people' in a group share a mental state without violating Rule 704(b)
The Supreme Court affirmed that expert testimony stating that "most people" in a particular group have a certain mental state does not amount to an opinion about whether the defendant had the charged mental state and therefore does not violate Federal Rule of Evidence 704(b). The decision resolves a dispute from the Ninth Circuit in favor of allowing such generalized expert statements.
Why this matters
The ruling clarifies the boundary between allowable expert background or behavioral testimony and prohibited opinions about a defendant's specific mental state. That affects how courts handle expert witnesses in criminal trials, including testimony from psychologists, sociologists, or other specialists who explain typical behavior or mental states in a group relevant to the charged offense.
Who may feel it
- Criminal defendants and prosecutors
- Trial judges who decide admissibility of expert evidence
- Expert witnesses (psychologists, psychiatrists, sociologists, etc.)
- Defense and prosecution attorneys
- Jurors who hear expert testimony
Key questions
- Does Rule 704(b) forbid an expert from testifying that "most people" in a particular group have a mental state relevant to the charged crime?