Also known as: experts in the field · expert witness · qualified expert
Written by attorneys · grounded in primary & secondary sources — see below
A specialist whose knowledge and practices determine whether facts or data are of a type reasonably relied upon by professionals when forming expert opinions. Courts use this benchmark to assess the permissible bases for testimony and the reliability of methods in fields such as genetic testing and forensic analysis.
Prosecutors call a forensic psychologist to explain a defendant's recorded statements after an alleged bank robbery. The expert begins to testify that the statements show the defendant formed the intent to commit the crime. The court sustains a defense objection and instructs the jury that only it may decide the mental state element.
In a murder prosecution the state offers a DNA analyst who relied on a profile generated by an outside laboratory. The defense objects on confrontation grounds. The court admits the testimony after finding the profile served only to explain the basis of the analyst's independent opinion and was not offered for its truth.
Select any source to read its text and confirm it supports the definition.
A paternity action requires genetic testing of the alleged father and child. The laboratory uses a method accredited by the AABB and routinely accepted by specialists in genetic testing. The court admits the results over objection because the testing satisfies the statutory reliability standard.
During a products liability trial an aerospace engineer testifies for the plaintiff. Defense counsel confronts the expert with a passage from an engineering treatise on wing stress. The court permits the passage to be read after the expert acknowledges the treatise as a reliable authority in the field.
A defendant charged with murder offers an expert to testify that a systolic blood pressure deception test proves the defendant was truthful. The court excludes the testimony because the underlying scientific principle has not gained general acceptance among specialists in the field of deception detection.
A plaintiff offers an epidemiologist who concludes that workplace chemicals caused his cancer. The expert relies on studies that do not address the precise chemicals at issue. The court excludes the testimony because the analytical gap between the studies and the expert's conclusion is too great.
An expert may disclose such facts or data when their probative value in helping the jury understand the opinion substantially outweighs any prejudicial effect. The court performs this balancing after confirming that specialists in the field reasonably rely on the same type of information.
No. The rule bars only a direct opinion that the defendant did or did not possess the required mental state. An expert may still describe data and draw intermediate inferences that stop short of announcing the ultimate mens rea conclusion.
Testing must be performed in a laboratory accredited by the AABB or by an accrediting body designated by the Secretary of Health and Human Services. The method itself must also be one reasonably relied upon by specialists in genetic testing.
…that the steering mechanism was broken. He said that the steering post was broken and that the steering gear was broken. An expert witness testified for the plaintiffs that he examined the car after the accident and found that the steering gear was broken. He said that the break was due to a defect in the manufacture of the…