But, however it is construed, the test as laid down in 1843 is insufficient in 1908.  Medical science has marched on with giant strides, while the law, so far as this subject is concerned, has never progressed at all.  It is no longer possible to determine mental responsibility by any such artificial rule as that given by the judges to the Lords in McNaughten’s case, and which juries are supposed to apply in the courts of today.  I say “supposed,” for juries do not apply it, and the reason is simple enough—­you cannot expect a juryman of intelligence to follow a doctrine of law which he instinctively feels to be crude and which he knows is arbitrarily applied.

No juryman believes himself capable of successfully analyzing a prisoner’s past mental condition, and he is apt to suspect that, however sincere the experts on either side may appear, their opinions may be even less definite than the terms in which they are expressed.  The spectacle of an equal number of intellectual-looking gentlemen, all using good English and all wearing clean linen, reaching diametrically opposite conclusions on precisely the same facts, is calculated to fill the well-intentioned juror with distrust.  Painful as it is to record the fact, juries are sometimes almost as sceptical in regard to doctors as they always are in regard to lawyers.

The usual effect of the expert testimony on one side is to neutralize that on the other, for there is no practical way for the jury to distinguish between experts, since the foolish ones generally look as learned as the wise ones.  The result is hopeless confusion on the part of the juryman, an inclination to “throw it all out,” and a resort to other testimony to help him out of his difficulty.  Of course he has no individual way of telling whether the defendant “knew right from wrong,” whatever that may mean, and so the ultimate test that he applies is apt to be whether or not the defendant is really “queer,” “nutty” or “bughouse,” or some other equally intelligible equivalent far “medically insane.”

The unfortunate consequence is that there is so general and growing a scepticism about the plea of insanity, entirely apart from its actual merits, that it is difficult in ordinary cases, whatever the jurors may think or say in regard to the matter, to secure twelve men who will give the defence fair consideration at the outset.

This is manifest in frequent expressions from talesmen such as:  “I think the defence of insanity is played out,” or “I believe everybody is a little insane, anyhow” (very popular and regarded by jurymen as witty), or “Well, I have an idea that when a fellow can’t cook up any other defence he claims to be insane.”