United States Sentencing Commission, Guidelines Manual, § 5H1.4 (2008).
“An extraordinary physical impairment may be a reason to depart downward;
e.g., in the case of a seriously infirm defendant, home detention may be as
efficient as, and less costly than, imprisonment.”

Debra Niehoff, Ties that Bind: Family Relationships, Biology, and the Law, 56 DePaul L.
Rev. 847 (2007).

Child abuse and neglect can cause chemical changes in the brain and
nervous system, with studies involving abused and neglected children
showing that “abused individuals were 1.8 times more likely to be arrested
for a juvenile offense, 1.5 times more likely to be arrested as an adult, and
1.35 times for likely to be arrested for a violent crime.” Id.at 847

Studies show that abuse “need not involve actual physical injury to do lasting
damage to the developing brain.” Id.at 849.

“Victims of abuse, the institutions charged with protecting them and the
criminal justice system would be better served if child welfare laws, policies,
sentencing guidelines, and treatment approaches were informed by a better
understanding of the impact of abuse and neglect on the human brain.” Id.
at 849.

“Clinical studies confirm that exposure to stress early in life – specifically, to
inadequate or abusive parenting – changes in emotional circuitry of the brain
and the neuroendocrine mechanisms underlying allostasis [the inherent
flexibility that allows functions such as rate and respiration to increase or
decrease to counter potentially destabilizing events] in enduring and often
compromising ways.” Id.at 855, 861.

Thomas M. Burton, Hidden Trauma: Studies Cite Head Injuries As Factor in Some Social
Ills: Brain Researchers Link Mental Woes, Alcoholism To Long-Ago Blows, Wall Street J.,
at A1 (Jan. 29, 2008).

“Researchers studying brain injury believe they've found a common thread
running through many cases of seemingly unrelated social problems: a
long-forgotten blow to the head. New research indicates hidden traumatic
brain injuries can cause social or educational failure, such as alcoholism or
homelessness.”

“They've found that providing therapy for an underlying brain injury often
helps people with a variety of ills ranging from learning disabilities to chronic
homelessness and alcoholism. If broadly verified, the findings could have a
significant impact in dealing with such intractable difficulties.”

“That severe head injuries can lead to cognitive and behavioral problems is
widely accepted. The U.S. Centers for Disease Control and Prevention
estimates 5.3 million Americans suffer from mental or physical disability that
is due to brain injury.”

“What's new is the contention of some researchers that there are many other
cases where a severe past blow to the head, resulting in unconsciousness
or confusion, is the unrecognized source of such problems. ‘Unidentified
traumatic brain injury is an unrecognized major source of social and
vocational failure,’” says Wayne A. Gordon, director of the Brain Injury
Research Center at Mount Sinai School of Medicine in New York, where
much of the research is being done.

John Paul Wright et al, Association of Prenatal and Childhood Blood Lead
Concentrations with Criminal Arrests in Early Adulthood, PLoS Medicine, Vol. 5, No. 5,
e101 doi:10.1371/journal.pmed.0050101.

Available at:
http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.p
med.0050101#toclink4

Study done by researchers at the University of Cincinnati.
“Prenatal and childhood blood lead concentrations were predictors of adult
arrests. . . . Data from several recent prospective studies suggest that blood
lead concentrations in the later preschool years may be more predictive of
cognitive and behavioral problems.”

“Environmental lead levels as well as crime have dropped over the last 30 y
in the US. However, the overall reduction was not uniform; inner-city children,
who are predominately African-American, remain particularly vulnerable.
Crime and violent crime are concentrated in urban centers in the US where
many poor African-Americans reside. One factor in the disproportional
representation of African-Americans in crime statistics could well be the
historically higher exposures to lead in these communities. Furthermore,
recent data from epidemiological studies implicate blood lead concentrations
well below the current level of concern adopted by the United States Centers
for Disease Control in the development of neurobehavioral deficits.”
“The neurodevelopmental consequences associated with lead exposure in
previous studies, such as lower IQ, less tolerance for frustration, deficits in
attention, hyperactivity, and weak executive control functions, are potent
predictors of delinquent and criminal behaviors. Attention deficit hyperactivity
disorder (ADHD) is a common finding among juvenile delinquents, and those
with ADHD are more likely to have severe cognitive impairments. ADHD is
also a known risk factor for criminal behavior in adulthood. A recent analysis
of data from the third National Health and Nutrition Examination Survey
(NHANES-III) found that higher blood lead concentrations were significantly
associated with ADHD. Children with blood lead concentrations greater than
2 _g/dl were at a 4.1-fold increased risk of ADHD. Similarly, in experiments
with rodents, felines, and nonhuman primates, early lead exposure was
associated with increased impulsivity, aggression, antagonistic interactions,
reduced social play and abnormal mother–infant interaction. Childhood lead
exposure therefore seems to place individuals at risk for multiple underlying
neurobehavioral deficits associated with a higher probability of later criminal
behavior.” (Emphasis added).

“Lead interferes with synapse formation, disrupts dopamine systems, and
lowers serotonin levels. Lead exposure has been shown to reduce MAO A
(monoamine oxidase A) activity, and low MAO A activity has been associated
with violent and criminal behaviors. One consequence of these alterations
could be neural dysfunction in areas of the brain involved in arousal, emotion,
judgment, and behavioral inhibition such as the prefrontal cortex.”