Harm, responsibility, and retributive justice

Chapter 11 endnote 3, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

The law is founded on the simple idea that you can choose to treat others well or badly. Choice bestows responsibility. If you treat others badly and consequently they suffer some harm, then you must be punished, particularly if you intended that harm. [...] The law distinguishes action, intent, and motivation.

What makes something a crime? Here are some important distinctions when deciding whether a crime has been committed:

• Was an action performed that caused harm (actus reus)?
• Was the action intentional? Did the person choose to perform the harmful action of their own free will?
• Was their a motivation to harm? Did the person perform the harmful action with the intent to cause harm?

“Intent” and “motivation” are about someone’s state of mind — did a person have a guilty mind (mens rea) for the crime.  Legal actors, such as judges and juries, infer a mental state when deciding guilt and innocence.

At the basis of this moral system of justice is Kant's view of morality, which can be summed up like this: "All things being equal, we have a general obligation to treat people well; but we are obliged to punish them when they deserve it." According to Kant, a person has free will to choose a course of action based on reason, and this makes a person intrinsically valuable (people are not worthwhile because they can serve a purpose or achieve a goal — they have value because they think, and this allows them to choose the right course of action).

There is a flip side, of course: when people choose to perform harmful actions, then they are responsible for those harms. Holding them responsible, and punishing them for a crime, is also an expression of society's regard for them and their free will. This is called retributive punishment, i.e., it is necessary to deliberately inflict pain on an offender if he is deemed morally responsibility for committing the offense. In this view, we sentence people, and send them to prison, out of our respect for their free will.

To Kant's way of thinking, torture is not acceptable, even for very bad crimes, because it strips people of their rationality and their ability to make a rational, moral choice.

Kant also wrote that people should be judged according to their moral standing. Anything that interferes with free will — perhaps a person can't control himself or is unaware that he has free will — makes a person less culpable for his actions. In the law, emotions are seen as interfering with free will.

The great hope is that brain imaging will do what reading facial expressions and polygraph tests have been unable to do:  read a person's mind.  But brain imaging cannot yet reveal someone’s state of mind. It's important to remember that the results of brain imaging experiments are based on a series of human choices.  Those beautifully colored images of the brain are curated by an experimenter.  Brains do not come conveniently color-coded.