The Connecticut medical examiner has asked scientists to analyze the DNA of Adam Lanza, the 20-year-old who killed 27 people, including his mother, two classrooms full of small children and teachers, before killing himself on Dec. 14.

Investigators hope that studying Lanza's DNA for mutations or other abnormalities may shed some light on the tragedy. Connecticut's chief medical examiner, Dr. H. Wayne Carver II, called the University of Connecticut a few days before Christmas asking for help from the UConn Health Center’s Department of Genetics and Developmental Biology, said UConn spokesman Tom Breen.

“They have agreed to offer any assistance they can to help the chief medical examiner in his investigation,” Breen said. Of Carver, Breen said, “He wanted help in conducting tests relating to genetics involving the shooter in the Newtown massacre.”

Breen said did not know what specific tests would be conducted. He said UConn was happy to help.

“This is such a terrible thing,” Breen said. “Everybody in the state has been affected by this.”

Will a DNA analysis help explain Lanza's rampage?

The study of Lanza's DNA would be for research purposes, not to find a diganosis for his acts, says Arthur Caplan, Ph.D, NBC News contributor and head of Division of Bioethics at New York University Langone Medical Center in New York City. While there has been prior research on genetic mutations and violent behavior, looking at someone’s genes "is like hunting in a DNA haystack," Caplan says.

"We don’t have a database that says there’s a correlation between genes and propenstity to violence or crime or propensity to mental illness," he says. "A particular DNA message may indicate a propensity to behavior, but at best you might find associations to greater risk. You won’t find a gene that says I’m going to be a mass murderer or a terrorist or an assassin."

James Fallon, a neuroscientist at the University of California, Irvine, who studies serial killers and other violent criminals, argues it will be fruitless to try to pin Lanza’s acts on his genes alone. Genetic data only paints part of the picture, he's found.

"The genes by themselves don’t tell you. If you just have a PET scan or MRI you can’t tell," Fallon said last week. "The psych report alone won't tell you. You put those things together you really get a lot of information." And some of what's been found by Fallon and other researchers provides some surprising insights.

Take for instance the “warrior gene”, the monoamine oxidase-A, or MAOA, gene that, has received widespread media attention, said Fallon.

“People know about the warrior gene and that it is associated with psychopaths and with killing,” Fallon said in a telephone interview.

Only a handful of diseases, such as cystic fibrosis, cause symptoms based on a single mutated gene. Most require thousands of changes and interactions. “So the idea that you have the warrior gene, therefore you are a warrior, it doesn’t hack it,” Fallon says.

It takes something more than just a genetic predisposition to make someone violent.

Fallon says there is no scientifically acceptable body of work on the genetics of violent behavior. "I don’t know of a case where even one killer has been studied genetically to an appropriate level, " Fallon said.

Likewise, brain studies have shed some light but can’t explain or predict the most extreme behaviors, said Dr. Martin Teicher, director of the Developmental Biopsychiatry Research Program at Harvard Medical School and McLean Hospital in Massachusetts.

“I don’t think we have the answer from neuroscience,” Teicher said. “Given the millions of people there are, the tiny handful of people who did these things are quite rare … We are drawing generalities from people who have had bad experiences, and who are maybe more prone to get into a fight, but they never would do anything like this.”

There is something that many violent people do have in common, however. Research done by Teicher, Fallon and others shows that violent criminals are, in fact, excessively anxious and fearful.

“Individuals at risk for violence often suffer from tremendous anxiety,” Teicher said. “It’s one of the most striking things I have noticed.” He’s treated high school students expelled or suspended for violence, but when they are in his office, they are anything but threatening.

“These are the frightening children in high school, yet they are essentially sitting in their mother’s laps,” Teicher said. “They were ridden with anxiety.”

And in some cases, this is combined with an inability to “read” other people. Teicher’s found this in some patients.

“We found differences in the (brain) cortex of violence-exposed individuals that play a role in social perception,” Teicher said. “These are regions involved in being able to infer what other people are thinking.” Brain scans show that the blood isn’t flowing normally in those brain regions. “They may be prone to misattribute thoughts and feelings,” Teicher says.

Such deficiencies can be immensely stressful to a young man or teenager, Fallon says. “He looks at people and doesn’t understand what they are feeling,” he said.

On top of this, Teicher has seen differences in parts of the brain’s frontal cortex that are involved in impulse control. “Misreading people and having difficulty controlling impulses may foster inappropriate actions,” Teicher says.

And while schizophrenia or bipolar disease do not usually lead to violent behavior, they can contribute to dangerous acts if patients are also racked with anxiety and not getting any sort of treatment.

“The late teens, early 20s, are when people have these psychotic breaks," Fallon said.

Most young people with these developing psychiatric conditions may feel anxious or threatened, but they don’t actually act on their feelings in part because they are unable to, Fallon said. Studies show the adolescent brain lacks the connections to initiate certain actions.

The brain is still growing, making new connections and cutting unneeded circuits, until the early 20s, Fallon said. The prefrontal cortex, involved in “executive function” or decision-making, is the last part of the brain to mature.

In an anxious young man, unable to understand people around him, perhaps ascribing all sorts of mistaken intentions to others, this could come to a climax, said Fallon, who studies how message-carrying chemicals such as dopamine and norepinephrine act in the brain.

The young man's brain is still growing and changing until, finally, the prefrontal cortex matures. The amygdala, the part of the brain responsible for fear responses on the most basic level, is at the same time being flooded with corticotropin-releasing hormone, which is involved in the brain's stress response.

“He is finally able to take action,” Fallon says. “Now the moment has come for him to carry out the ultimate act. If you turn it around like that, it makes a lot of logical sense."

Lisa Flam contributed to this story.

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