Nathan Dunlap, 38, right, with attorney Madeline Cohen, appears at a hearing at Arapahoe County Court in Centennial, Colo, Wednesday, May 1, 2013. Dunlap's attorneys asked a judge Wednesday to delay designating a week for execution, saying Dunlap's death sentence was meant to be served only after he completed a 75-year sentence for robbery. Dunlap is convicted of killing four people at a Colorado pizza restaurant in 1993. (AP Photo/The Denver Post, Helen H. Richardson, Pool)

AURORA | Nathan Dunlap’s lawyers on Monday formally asked Gov. John Hickenlooper to spare the convicted killer’s life.

In a 25-page clemency petition filed Monday morning, Dunlap’s defense team said his diagnosed bipolar disorder, family history of abuse and mental illness, as well as the flawed way Colorado uses the death penalty mean the governor should let Dunlap spend the rest of his life behind bars.

Nathan Dunlap, 38, right, with attorney Madeline Cohen, appears at a hearing at Arapahoe County Court in Centennial, Colo, Wednesday, May 1, 2013. Dunlap's attorneys asked a judge Wednesday to delay designating a week for execution, saying Dunlap's death sentence was meant to be served only after he completed a 75-year sentence for robbery. Dunlap is convicted of killing four people at a Colorado pizza restaurant in 1993. (AP Photo/The Denver Post, Helen H. Richardson, Pool)
Nathan Dunlap, 38, right, with attorney Madeline Cohen, appears at a hearing at Arapahoe County Court in Centennial, Colo, Wednesday, May 1, 2013. Dunlap’s attorneys asked a judge Wednesday to delay designating a week for execution, saying Dunlap’s death sentence was meant to be served only after he completed a 75-year sentence for robbery. Dunlap is convicted of killing four people at a Colorado pizza restaurant in 1993. (AP Photo/The Denver Post, Helen H. Richardson, Pool)
Nathan Dunlap, 38, right, with attorney Madeline Cohen, appears at a hearing at Arapahoe County Court in Centennial, Colo, Wednesday, May 1, 2013. Dunlap’s attorneys asked a judge Wednesday to delay designating a week for execution, saying Dunlap’s death sentence was meant to be served only after he completed a 75-year sentence for robbery. Dunlap is convicted of killing four people at a Colorado pizza restaurant in 1993. (AP Photo/The Denver Post, Helen H. Richardson, Pool)

And, the lawyers said, Dunlap is sorry for killing four people and wounding a fifth during a 1993 robbery of an Aurora Chuck E. Cheese restaurant.

In the petition, Dunlap wrote that he is remorseful for what he did as a 19-year-old.

“I’m just sorry for everything that happened on December 14, 1993 and the ripple effect that followed,” he wrote. “As I’ve put my thoughts and feelings to paper, I know saying, writing, and feeling sorry isn’t enough and I wish there was something more that I could do to relieve any pain.”

A judge last week scheduled Dunlap’s execution for August.

Several courts in Colorado and at the federal level have upheld Dunlap’s death sentence, leaving a plea to the governor as the defense’s only hope of sparing his life.

The Associated Press reported Monday that Hickenlooper is holding private meetings on Friday and Saturday on the Dunlap case. Spokesman Eric Brown says he’s hearing information from all sides.