Neurolaw: Confusing intent with motive is a threat to civil rights

Re the problem with "neurolaw" (the attempt to scan brains to identify criminal behaviour), I have said this before, but it is worth repeating in the context: Law is, or should be, concerned with "intent", not "motive."

Yes, yes, in detective fiction, everything hinges on motive: Cousin Harry murdered Aunt Sally to get her fortune; plain Jane murdered pretty Kitty because Kitty got the man; squadron leader Beeder murdered that guy because of a long ago wartime betrayal ....

However, real law depends in design inferences, not speculations about motive. Here is the story I sometimes tell to explain that:

Tom and Dick are enjoying beer and wings in a pub.

Suddenly, the conversation becomes loud and animated.

Tom seizes a dinner knife and tries to plunge it into Dick's chest. He is restrained by burly patron Harry and several others.

The whole thing is caught on videocam.

Mid-uproar, someone calls the police, and they charge Tom with attempted manslaughter.

The police need not know his motive, only his intent - which was pretty obvious. That's a design inference.

Later, the investigating officer learns how the quarrel began: Dick had informed Tom that he was seeing Tom's girlfriend, so Tom should just buzz off. Tom didn't like that idea.

Knowing a person's motive certainly helps us understand the story. But intent - the demonstrated attempt at murder in this case - is what matters in law.

Here's the difficulty: Suppose Tom had just got up from the table and left, and spent three months fantasizing in the wee hours about killing Dick - without ever seeing either Dick or the former girlfriend again. He has plenty of motive, but the fact is, he never did anything.

Then Tom is of no interest to the law, as it now stands - though his family doctor should be concerned. Tom needs a more constructive way to deal with rejection. (He also needs a more faithful girlfriend, but all in good time.)

However, in a materialist environment, I would hardly be surprised to hear theories about Tom's violence genes and violence neurons, some based on neuroscience techniques - even if all the violence was inside his own head.

Some may argue for action against Tom "pre-crime". That's where the threat to civil liberties comes in.

Neurolaw seems like materialism applied to law, hence a threat to civil rights, because it can easily confuse motive with intent - overturning centuries of progress in justice.