After someone kills someone, how they behave in jail depends on their motivation for committing the crime, said forensic psychologist Charles Robinson of Manchester in a phone interview Wednesday.

Robinson was retained to do a forensice exam of Christian C. Nielsen, according to a motion filed Oct. 19 by defense attorney Ron Hoffman, but he has not confirmed he’s involved in the case.

Robinson said Wednesday that motives can be classified in two categories – instrumental, where the person has a purpose in mind for killing his or her victim; or emotional, where the person has a relationship with the victim and often kills someone they love.

Those who are emotional killers tend to have more regret while in jail awaiting trial. They’ll act remorseful and try to busy their minds to avoid thinking about it, which is difficult in jail, Robinson said.

These people are prone to post-traumatic stress disorder, depression and have a higher risk of harming themselves, Robinson said.

Those who kill for instrumental purposes tend to have a sense of accomplishment, Robinson said, because they did what they meant to do.

People accused of murder have a high risk of being harmed by other inmates, Robinson said.

Those who had not been incarcerated before have a high risk of mental illness, because they are not allowed as much social activity, and become frightened and claustrophobic. They can have trouble sleeping, which also affects behavior.

Whether or not the person had pre-existing mental conditions, all are subject to developing mental illness, Robinson said.

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