What is the test for determining whether a jury should consider a defendant's mental state as a mitigating factor in determining the penalty?

20 Defendant also relies upon State v. Robinson (1991) 330 N.C. 1, 409 S.E.2d 288, 305-308, which considered the effect of an erroneous instruction requiring the jury unanimously to find the existence of a mitigating factor before it could consider such a factor in determining the penalty. Because this error might have prevented consideration of evidence concerning the defendant's mental age, the appellate court, in deciding whether the error was harmless, examined whether the jury necessarily considered such evidence in connection with other factors. The court simply held that the jury's finding with regard to a factor based upon the defendant's intoxication or mental condition did not establish that it necessarily considered his mental condition as a mitigating factor. Contrary to defendant's assertion, this decision does not hold that the jury specifically must be instructed to consider mental age as a separate mitigating circumstance.