State v. Thomas

To be admissible, an expert’s opinion on diminished capacity must be helpful to the trier of fact in assessing the defendant’s mental state at the time of the crime. An expert does not have to testify with reasonable medical certainty that the mental disorder actually caused diminished capacity at the time of the crime, but the expert must be able to testify based on reasonable medical certainty that the defendant suffers from a mental disorder that impairs the defendant’s ability to form the requisite intent to commit the crime. In this case, the expert witness would testify that it was…