Gunman Adam Lanza will have his DNA tested to find out if it carries an “evil” gene.
The study on Lanza, who shot dead 20 children and six adults at Sandy Hook School, is thought to be the first carried out on a mass killer.
The study has been ordered by Connecticut medical examiner H Wayne Carver who carried out post-mortems on the victims.
Geneticists said they are likely to look for mutations or abnormalities that could increase the risk of aggressive or violent behaviour.
Professor Arthur Beaudet, of Baylor College of Medicine in Houston, Texas, said: “I don’t think any one of these mutations would explain every mass shooting…but some would have mutations that cause schizophrenia and related violent behaviour.”
He added he hoped it would lead to the development of “treatment to stop” mass shootings.
Earlier, Mr Carver said he was seeking genetic help to find “any identifiable disease associated with this behaviour”.
The massacre two weeks ago…which claimed the life of Brit Dylan Hockley, six…has prompted Barack Obama to investigate tightening US gun controls…but that’s all President Obama ever says. He’s always going on about what should be done…but in the end…does nothing. Are people still ‘wowed’ because he is the first black president? Americans can’t be that stupid…can they?
After the last shootings, President Obama gave a speech about ‘investigating gun-law’, and telling us what ‘should be done’…
Are we going to have to wait for more shootings…or will it be quicker to wait for another president who actually acts, so that Americans can believe that their leader DOES want to protect them?
Police have yet to find a motive. Lanza, 20, also shot his mother and killed himself.