"Glue has certain toxic substances in it, and in this particular case, his abuse of the glue damaged certain parts of his brain that was intimately involved in his actions and affected his capacity to inhibit his impulses, and also led to a mental state that essentially caused him to be sort of out of touch with reality during the time when the crime was committed." During the capital case, remembers Heilbronner, the prosecution withdrew the death penalty but sentenced the individual to a life term.
Lawn care employee David Garabedian wasn't so lucky. Back in 1986 Garabedian was charged in the strangling of customer Eileen Muldoon. The defense claimed Garabedian's violent behavior had been the result of involuntary chemical intoxication brought on by contact with lawn care chemicals used in his job.
Dr. David Bear, the Vanderbuilt Medical School physician who looked into David's case, went on to say the chemicals in their undiluted form caused physical and mental changes in David's body, poisoning the enzyme that clears away acetylcholine in the hypothalamus thus inhibiting Garabedian's aggression-control and accounting for his overwhelming rage. The case was recently reopened for trial; however, the poisoning plea was rejected by jurors and in February 2009 Garabedian was convicted of first-degree murder.
In our vast synthetic-laden society, chemicals are increasingly being studied for their impact on the brain and behavior. The Learning Disabilities Association of Canada cites lead and immoderate alcohol use as being among the environmental agents that can cause aggression and impulsivity during infancy or even presenting later in life.
High levels of copper and zinc are also being linked to learning disabilities and aggression. In a study titled "Elevated blood copper/zinc ratios in assaultive young males" performed by the Health Research Institute in Naperville, Illinois, researchers found that the copper to zinc ratio was higher in subjects with a history of aggravated assaults and lower in those with a history of verbal assaults. It went on to suggest that "chemical imbalances in the body could be as important an influence as poverty, abuse and other environmental factors traditionally accepted as the predominant cause of deviant behavior."
Knowledge as protection
Hartman says such scenarios can present very complex questions in court, especially because jurors must wrestle with violent intent, whether they're dealing with someone who is impaired by legal definition or someone who is performing a calculated action for an expedient result.
"All of those things are potentially what you have to think about when you are looking at the end result of violent action," says Hartman. "Because violence is really only the very last behavioral outcome; there are any number of things that can lead to it: some social, some purely brain-related some emotional. And working backwards from that behavioral act is really the science of forensic neuropsychology, and it's been the subject of many clinical studies.
"For everyone who in some way commits a violent act, you can't rubber stamp the answer," says Hartman. "You have to work backwards in the crime and ask yourself as a forensic clinician what combination of behaviors might be causal to the end result."
Cases like the Garabedian murder are not common, but they do happen. And Hartman emphasizes it's still important to look at each case based on its individual merit. "All sorts of causal information is useful," he says, "as it helps us figure out common pathways and what interventions may be possible."
Stephen Morse, Professor of law and psychology at the University of Pennsylvania, likens research of the brain to wearing a bicycle helmet. "We know something about what happens when the head gets knocked, and that helps us to take steps to prevent these things from happening in the first place. Or, to use a different example, [studying the brain and behavior may prompt us to] get the lead out of paint.
"We know what causes HIV and AIDS, but so far we can't do much about it," says Morse. "But, knowing what the HIV virus is may someday lead to a vaccine or to a better treatment. This is very useful knowledge."