d. The ultimate issue

d. The ultimate issue

It has long been said that there is a so-called “ultimate issue rule”, i.e. an expert is not permitted to testify on the ultimate issue of the case. It reflects the traditional understanding that experts are to educate the jury in the fact-finding process. The jury should not be invited to defer to the conclusion of the experts.

In other words, an expert is not entitled to conclude that “the defendant is guilty”, or that “the defendant had contact with the packet of cocaine”. The expert should, for example, only give opinion how he or she had found that the fingerprints retrieved from the packet of cocaine matched with the defendant’s fingerprint.

In practice, it would be artificial, if not only difficult, to ask experts not to give an opinion on the ultimate issue. An expert may inevitably give an opinion, but the presiding judge must warn the jury that they are not bound by the expert’s opinion, and that the issue is for them to decide.