Does Brain Scan Evidence Help or Hurt at Sentencing?

Brain evidence can help and hurt at sentencing. Evidence of a brain disorder may lead to less prison time, but it may also lead to more time in a hospital.

Why defense lawyers use brain evidence

Defense lawyers are using brain evidence more often in U.S. criminal cases. Scans such as an MRI or CT scan can show damage, abnormalities, or disorders that may help explain why a person committed a crime. That can be a reason for a lighter sentence.

One study of court opinions found brain or behavioral science evidence raised in about 5% of murder cases and about 25% of death penalty cases. When there is evidence that a person could not fully control his actions because of a brain disorder or mental illness, courts may be more willing to give a lighter sentence.

There is a catch. Research suggests decision-makers may give less prison time but more mandatory hospitalization. So this evidence has to be used with a delicate touch. The goal is to lower prison time while keeping the chance of hospitalization from going up.

An experiment on how people react to brain evidence

It makes sense to go easier on someone who could not fully control what he did. The law already does this in several ways:

• Self-defense, or defense of others, can be a complete defense to a crime.
• Insanity can be a complete defense.
• "Heat of passion" can reduce a killing to a lesser crime when the person lost control in the moment.

Researchers wanted to test that instinct with data. In one experiment, 330 volunteers read a summary of a sexual assault case and recommended a sentence, which gave a starting point.

Next, they were told the defendant had either a neurobiological (brain-based) or a psychological disorder, and that it was either treatable or untreatable. The volunteers could then change their sentence, choosing prison, mandatory hospitalization, or both.

What the experiment found

The volunteers trusted brain-based evidence more than psychological evidence. They gave the most leniency to defendants described as having a neurobiological disorder.

But that leniency came with a cost. A neurobiological disorder led to shorter prison terms and longer hospitalization terms. That is the double-edged sword of brain evidence.

Treatability mattered too. A treatable disorder led to both shorter prison terms and shorter hospital terms than an untreatable one.

What this means for sentencing

People weigh two goals at once: justice and public safety. When someone chose to do wrong, we want punishment. When someone could not control himself, we still want to protect the public.

That makes brain evidence a challenge for defendants and their lawyers. Like squeezing a balloon, it may reduce prison time while increasing hospital time. One lesson from the study is that evidence a condition can be treated may matter as much as the diagnosis itself. If your family member has a documented brain injury or mental illness, collect the medical records and any treatment history early so the defense can decide whether, and how, to use them.

Going forward, courts and lawmakers will need to decide how best to handle evidence of brain disorders. They will need to help sentencing judges "separate the wheat from the chaff" when judging whether this kind of evidence is credible, accurate, and valid.

Facing a federal sentence? Book a consultation to talk it through with Brandon Sample.