PORTSMOUTH, N.H.

MICHAEL ADDISON, 28, was sentenced to death by a jury on Dec. 18 for the shooting death of Manchester Patrolman Michael Briggs, opening the door for the first execution in New Hampshire since 1938.

Briggs, 35, and a bicycle patrol partner came upon Addison and friend Antoine Bell-Rogers in an alley in 2006. Recognizing the men as suspects in a recent shooting and two armed robberies, he ordered them to stop, before Addison shot Briggs in the head at close range, according to court testimony.

Addison’s lawyers argued that an abusive childhood and possible brain damage from exposure to alcohol in the womb warranted a sentence of life in prison without parole, but jurors did not see it that way and decided on the death penalty.

The sentence could be argued from more than one side.

Heavy-handed penalties such as death are not handed down with great precision. After all, the death penalty is not uniform across states; 14 states do not have it while the rest do, and jurors deliberate with their own internal frameworks to decide if it’s right.

Legal precedents can count for only so much, and many questions often remain about how the fitness of a sentence is reasoned.

Two models are used to evaluate the appropriateness of a death sentence: deterrence and justice.

The argument from deterrence sees crime as a utilitarian matter of public health with a death penalty serving to deter crime from happening. But researchers have not made a conclusive connection between the death penalty and crime rates. It therefore cannot be the defining factor in a decision.

The argument from justice sees crime as a moral wrong that requires a death penalty to be carried out as a tit-for-tat retribution that conveys a concept of justice.

The meaning of such payback is often obscure and often connotes something closer to revenge, a function obviously different than justice. It is important to stick with the original sense of the term, and here it is clear that the death penalty is not a payback: The dead can be paid nothing.

This doesn’t leave much of a case for the death penalty. It also doesn’t tell us how to handle a murderer.

The progress of science can make decisions more difficult, not easier.

The legal system is now growing out of age-old dichotomies of guilty/innocent, sane/insane, life/death into a more nuanced framework, and it’s doing so with help from philosophers.

The MacArthur Law and Neuroscience Project, a $10 million research effort headed by Walter Sinnott-Armstrong, a philosopher at Dartmouth College, is setting out to create recommendations for the use of neuroscience in the legal system. It seeks to inform a more sophisticated code of treatments and penalties.

Project members want to clarify ways neuroscience can be used to define the criteria for how brain impairment can reduce the space in which a person can make a clear choice; criminal responsibility; the predictability of crimes, and the treatment and punishment of criminals, Sinnott-Armstrong said.

Most of the contributors to the project begin on assumptions that judgment varies in degrees.

“That certainly strikes me as the case,” he said. “The vast majority of us believe that at least some people, and, indeed, most people, are responsible for their actions. But when we look at cases from a scientific perspective, we see a variety of conditions and . . . people’s abilities vary in increments.”

A more nuanced system and MRI machines in a courtroom could give a clearer indication of how free Michael Addison, a man with possible brain damage, was in his actions.

Such a system does not forgive a deplorable action. It does not return us to the simpler days of the 1960s and 1970s, when the prison-reform movement asserted that bad upbringings made inevitable many convicts’ criminal actions.

It promises treatments far more nuanced and based on biologically driven models, the use of neuroscience for intervention and prevention, better placement of inmates, and more nuanced sentences. Neuroscience cannot undo many actions but it does give us a brighter hope for public health.

Jim Kozubek is a New Hampshire-based writer.