In this recent criminal case won on NJ appeal, the defendant convinced the appeals court that his expert witness should have been allowed to testify that he was a drug addict. This would have assisted the defense that drugs found on his person were for personal use and not for sale.
State v. Ryshan Tatum, unpublished opinion, App. Div. Docket No. A-1313-08T4 (December 23, 2009) - Convictions reversed following remand for hearing on whether expert's opinion could be of assistance to the jury.
"Although the judge found that McCorkell qualified as an 'expert in alcohol and substance abuse counseling with an expertise in therapy and counseling,' he concluded that McCorkell's testimony would not have been of assistance to the jury, or that even if it would, it would not have affected the result of the case.
We disagree with the first proposition and find the second proposition irrelevant under the Supreme Court's remand order.... The average juror would not know about the standards for determining drug addiction set forth in the DSM-IV. Thus, an expert's opinion applying those standards to determine if defendant was a drug addict would be useful in deciding whether that was so or not.
Since in this case, the defense was that the drugs were for personal use, defendant's status as an addict would obviously be relevant. Of course, drug addicts can and often do sell drugs to support their habit, but if a defendant was a drug addict at the time of the offense, it is at least more likely that he had the drugs for personal use....
Since McCorkell's testimony could be of assistance to a jury and since it cannot be barred simply because he relied on the kind of hearsay that experts in his field rely on, and because he did not squarely address the substance of Graves's testimony, we are obliged to reverse and remand for a new trial."
http://www.judiciary.state.nj.us/opinions/a1313-08.pdf
