By Jonathan Allen

NEW YORK (Reuters) - The second suspect in a brutal 2007 Connecticut home invasion is a damaged human being but is not "pure evil," his lawyers said, arguing such descriptions by the victims' family threaten his right to a fair trial.

Joshua Komisarjevsky is accused of murdering Jennifer Hawke-Petit and her daughters Hayley, 17, and Michaela, 11, and beating her husband, Dr. William Petit, in a home invasion described as one of the most brutal attacks in Connecticut memory.

In court papers unsealed on Monday, lawyers for Komisarjevsky said he should be spared the death penalty, and that the "provocative language" of the Hawke-Petit's loved ones was impinging on their client's right to a fair trial.

"Contrary to the families' aspersions, however, Mr. Komisarjevsky is not 'pure evil'. He has displayed remorse, and his execution would not advance justice, as that concept is defined in most of the civilized world," the defense team said in an extrajudicial statement.

After a jury trial last year, Komisarjevsky's alleged accomplice, Steven Hayes, was convicted of the triple murder and sexual assault and sentenced to death.

Komisarjevsky's lawyers criticized public comments made by the victims' family, including in a memoriam published in New Haven newspapers and in an interview on the Oprah Winfrey Show describing both men as evil and deserving of the death penalty.

Komisarjevsky's lawyers, in the document, say their client was a "damaged human being" and suggest he had a mental disorder following years of trauma and abuse. They said he wants to avoid the death penalty and spend the rest of his life in a maximum-security prison.

Prosecutors have already said they have no plans to offer Komisarjevsky a plea deal that might spare his life. Connecticut's last execution, the only one since 1960, was in 2005, according to state authorities.

According to prosecutors, Komisarjevsky and Hayes decided to rob the Petit home in Cheshire, Connecticut after targeting Hawke-Petit at a local grocery store.

Breaking into the family's home in the middle of the night, the assailants found Petit asleep, beat him and tied him up.

After being held for several hours, Petit escaped the house, at which point the attackers sexually assaulted and killed Hawke-Petit, sexually assaulted the youngest daughter and set a fire that killed the two girls.

Komisarjevsky's lawyers said there were reasons their client was in the house on that night that will become known if the trial opens as scheduled on September 19.

(Editing by Barbara Goldberg and Cynthia Johnston)