The jury shouldn't be deciding legal questions - that's for the judge. A jury is supposed to come to their verdict on a consideration of "matters of fact" (a term of art in the law).
For example, the definition of a particular offense (Grievous Bodily Harm, say) is a matter of law, and not up for debate by the jury. The jury's role is to decide whether or not the accused committed that particular crime; eg, does the evidence support ("beyond reasonable doubt") the conclusion that they throw the punch that the prosecution allege caused the injury to the accuser?
For example, the definition of a particular offense (Grievous Bodily Harm, say) is a matter of law, and not up for debate by the jury. The jury's role is to decide whether or not the accused committed that particular crime; eg, does the evidence support ("beyond reasonable doubt") the conclusion that they throw the punch that the prosecution allege caused the injury to the accuser?