March is Brain Injury Awareness Month in the United States. And although traumatic brain injuries (TBIs) affect millions of Americans, a comparison between the general U.S. population and the country’s prisoners provides a stark differential.
While a significant 5% of Americans live with TBIs, a National Library of Medicine study puts the figure among the incarcerated population at between 50% and 80%.
This study will dig deeper into the data to look at the effect a TBI has on cognitive function and behavior, what causes TBIs, how this manifests, and what substantiates the link between TBIs and criminal behavior.
As the study will show, TBIs are a highly relevant factor when assessing criminal behavior and are often referenced during court testimony as mitigation regarding a violent act. Let’s consider why this is the case.
TBIs and Criminal Behavior
With more than two million people in the U.S. currently locked up (and millions more in justice system limbo, either on probation or under supervision), understanding the significance of TBIs among the prison population is of potentially key significance.
This is true not only from a medical vantage, but also to help us better understand and anticipate the causes or exacerbating factors behind criminal behavior.
But what characterizes a TBI? According to the Centers for Disease Control and Prevention (CDC), these three broad categorizations of brain trauma all apply.
- A mild brain injury is classified as one that subtly alters mental status and/or leads to a loss of consciousness of up to 30 minutes.
- A moderate brain injury might involve unconsciousness lasting from 30 minutes to 24 hours.
- A severe brain injury refers to a blow leading to unconsciousness that lasts longer than 24 hours (coma).
We’ve already noted that 50%-80% of people in prison have experienced some form of TBI. However, according to the Compassionate Prison Project, that’s a cross-gender measure: if we limit our focus to the female prison population, that number is as high as 97%, mainly due to strangulation from domestic violence, which can inadvertently injure the brain.
We’ve also briefly mentioned the use of neurological evidence (such as magnetic resonance imaging (MRI) scans) in court to help determine the extent to which brain damage may have induced a person to commit a violent act.
This type of evidence was introduced in 12% of all murder trials and 25% of death penalty trials between 2014 and 2024.
TBI and Criminal Law
In criminal law, a defendant’s mental state is a central factor when it comes to determining their legal responsibility. Courts frequently rely on two key components—the cognitive and volitional prongs—to assess whether a defendant could understand and control their actions.
The Cognitive Prong
This prong focuses on a defendant’s ability to comprehend the nature, quality, or wrongfulness of their act. When traumatic brain injury affects memory, judgment, or reasoning (especially in areas of the brain responsible for executive function) a person may fail to appreciate the moral or legal consequences of their behavior.
Even if they appear coherent or articulate, underlying neurological damage can significantly distort their perception of reality or the consequences of their actions.
The Volitional Prong
This examines whether a defendant could control their errant behavior. While a person may comprehend that what they’re doing is wrong, damage to brain regions such as the prefrontal cortex may limit impulse control. This impairment to inhibition, common in moderate to severe TBIs, can result in abrupt, spontaneous violence.
In cases involving brain injuries, expert testimony and neuropsychological assessments are often essential to demonstrate how a defendant’s condition affects either or both prongs. These evaluations also help to determine whether or not a defendant is competent to stand trial. Brain injuries may limit their ability to understand proceedings.
Numerous studies have established compelling data around the link between TBIs and aggression, violence, and criminality. Let’s consider some of the examples.
TBI and Aggression
W.A. Gordon’s study found that a history of TBI is associated with increased aggressiveness, drug and alcohol use, cognitive functioning disorders, and antisocial behavior. This study focused on TBI survivors and their cases, and found that 60.25% of adult criminal offenders had experienced at least one TBI.
The study also found that the age of the person when they first suffered an injury was a key predictor of aggression following head trauma: the younger the individual suffering from trauma, the more likely they subsequently were to become aggressive.
And, of 4000 juvenile delinquents screened for TBI, trauma was notably common in these individuals: 21.9% of the state sample and 41.3% of the county sample met the criteria for at least one TBI.
A highly significant result of this particular study is the proportion of delinquent participants who had suffered a TBI and subsequently committed a criminal offence (state, 56.5%; county, 78.5%). Additionally, those who had suffered a TBI exhibited an aggression rate of 25%; to compare, the rate among the general population is 2-13%.
Another study – this one from the University of Iowa Hospitals and Clinics – found that of 89 patients who had suffered a TBI, 30 (33.7%) subsequently met the criteria for significant aggressive behavior during the first six months following the traumatic episode. The remaining 59 patients (66.3%) constituted the nonaggressive group.
Neuroimaging studies have identified the areas of the brain most affected by TBI that may subsequently influence deviant behavioral changes.
- In one study, 64.5% of examined murderers were found to have frontal lobe dysfunction, while approximately 47% reportedly also had abnormal neuroimaging.
- The amygdala and insula are two brain regions widely believed to be involved in the regulation of aggressive behavior, while prefrontal areas such as the orbitofrontal cortex (OFC) serve to inhibit aggression. Damage to these regions can compromise the balance of this inhibition system and can negatively influence behavior.
- Frontal lobe dysfunction has been used as mitigation regarding the uninhibited actions of people charged with or convicted of violent crimes.
- A lack of empathy and remorse has been correlated with bilateral damage to the amygdala, while violence has also been attributed to abnormal electrical activity in the amygdala.
- Individuals with orbitofrontal injury disproportionately displayed antisocial traits (disinhibition, impulsivity, lack of empathy) that ultimately led to the diagnosis of ‘acquired sociopathy’, while some were subject to an increased risk of violent behavior.
And a prison survey found that, of 196 male offenders, over 60% reported ‘Head Injuries’, while 65% gave injury explanations consistent with various types of TBI.
Of the overall sample, 16% had experienced a moderate-to-severe TBI, with 48% subject to a mild TBI. Adults with TBI were younger at entry into custodial systems than prisoners without, and reported higher rates of repeat offending; they also observed longer prison sentences over the previous 5 years.
The study concludes: ‘These findings indicate that there is a need to account for TBI in the assessment and management of offenders.’
To further emphasize the link between TBIs and criminality, it’s also worth considering the arrest discrepancy between those suffering from TBI and those clear of any TBI issues.
TBI and Arrests
About 2% of the general population is arrested every year. According to Brooks et al, during the five years following an initial brain trauma, 31% of survivors of TBIs had been in trouble with the law at least once (but usually multiple times).
They also described 64% as suffering from a bad temper, and 54% as having threatened violence. While a person may have been calm and controlled before a TBI injury, they may subsequently become quick-tempered and lack inhibition.
This research established a similar rate of arrest (one-third) in a community sample of children and adolescents with TBI. The correlative patterns continue to stack up when we look at the most serious criminals of all – those on death row.
Death Row TBI Studies
A study (1986) of 15 U.S. death row inmates found evidence of brain impairment in 100% of the cases. A subsequent study (1988) of 37 U.S. juveniles awaiting execution, 14 had histories of head injury with associated signs of neurological dysfunction.
Sadly, while the findings were relevant to mitigation appraisals, they were not identified or presented in the trials, during sentencing, or in the course of subsequent appeals.
A Freedman and Hemenway (2000) study also suggests that men on death row tend to have neurological, psychiatric, and psychoeducational issues. In their case-study analysis of the social and family histories of 16 men on death row, they found a compelling history of brain impairment or mental illness in all cases (while 12 had a confirmed history of TBI).
TBI State Differentials
In many cases, TBIs cause fatalities. But a preponderance of high TBI fatality rates in an area may indicate a populace more vulnerable to and suffering from a wide variety of TBIs.
Here are the U.S. states that feature the highest number of fatal TBIs (per 100,000 of the population, 2023 data).
Some demographics are far more susceptible to TBIs than others. Here are some key examples.
People At High Risk of TBIs
Homeless People
According to study data, compared to the general population, homeless people are:
- 2 to 4 times more likely to have a history of any type of TBI
- Up to 10 times more likely to have a history of a moderate or severe TBI.
Homeless people with a history of TBI are far more likely to suffer worse overall physical and mental health, and are also more likely to have experienced violence and/or trauma during childhood.
Survivors of Intimate Partner Violence
Domestic violence victims who suffer a TBI due to an assault are more likely to be diagnosed with PTSD, insomnia, and depression, and to report worse overall health.
People with Lower Incomes/Without Health Insurance
Economically vulnerable people are far less likely to receive a TBI procedure (such as craniectomy/craniotomy, ventriculostomy, intracranial pressure monitor placement, arterial line placement, or central line placement). They’re also:
- Less likely to receive inpatient services, such as rehabilitation
- More likely to die in the hospital.
People in Rural Areas
Rural residents are at a higher risk of dying from a TBI than people living in urban areas. This is because:
- They need to cover longer distances when they travel between a residence and an emergency medical care center
- They have less access to a level I trauma center.
Understanding TBIs And Their Link To Changing Behavior
Traumatic brain injuries affect many members of the general U.S. population, with a reported 5% living with TBIs. Yet when we compare that percentage with the proportion of the incarcerated population suffering from TBIs (50-80%), it suggests a compelling link between brain injury and criminal behavior.
That’s not to say that TBIs directly cause crime: instead, it suggests that some types of TBI can mean some of those suffering from trauma are more likely to commit acts of crime.
The data further augments the link between criminal behavior and TBIs via numerous close case studies. Combined, the studies suggest that a TBI can mean less inhibition and more aggression, and that early trauma worsens the overall outlook and makes criminal behavior more likely.
With MRI scans now an established part of defense mitigation, it’s clear that TBIs are a significant aspect of criminal appraisal.
The age of the person when they first suffered an injury was a key predictor of aggression following head trauma: the younger the individual suffering from trauma, the more likely they were to become aggressive
By understanding the dire potential effects of TBIs, better awareness of the problem can lead to greater understanding – and far better prevention of violent criminality.
So, grasping the potential permutations of a TBI can mean bringing down crime numbers, depopulating teeming prisons, and making society safer. TBIs represent a serious national health issue. Early diagnosis, the right medical treatment, and ongoing mental health support are all crucial parts of the preventative equation.
Ultimately, a better appreciation of TBIs and their actual and potential effects adds an important dimension to broad conversations about criminal justice reform, rehabilitation, and public health policy.
By learning about the physical problems that in many cases facilitate dangerous behavior, we can pre-empt it and save lives, injuries, and immeasurable levels of individual and familial torment.
Violent crimes are treated very seriously by California courts. If the police accuse you of a violent illegal action, you could be facing extensive fines, marks on your criminal record, and years in jail. However, you might be able to avoid a harsh sentence for a white-collar crime conviction.
A Los Angeles violent crimes lawyer from Simmrin Law Group can help you with your case. You can contact one of our experienced Los Angeles criminal defense lawyers to get professional support after an arrest.