(CNN) -- Jared Loughner, the Arizona man who pleaded guilty to the attempted assassination of then-U.S. Rep. Gabrielle Giffords, will be sentenced Thursday.
Federal prosecutors have said Loughner will be sentenced to life in prison without the possibility of parole for the January 2011 shooting, which killed six people and wounded 13 others, including Giffords.
The congresswoman was holding a meet-and-greet event with constituents in Tucson when Loughner walked up and shot her in the head.
Giffords stepped down from her position in Congress in January 2012 to focus on her recovery and has since regained the ability to speak and walk, though her right side remains weak.
Giffords and her husband, retired astronaut Mark Kelly, plan to appear in court for the first time in the case, a source close to Giffords said, adding Kelly plans to speak on behalf of the family.
As part of a plea deal with the government, Loughner, 24, pleaded guilty in August to 19 charges in exchange for the sentence to avoid facing the death penalty.
Loughner had been facing more than 50 federal charges, and the remaining offenses were dropped in exchange for the guilty pleas if Loughner is sentenced within the terms of the plea agreement, according to a written agreement filed in court.
Under the pleas, Loughner admitted guilt in the wounding of Giffords and the murders of federal employees U.S. District Court Chief Judge John M. Roll, 63, and congressional aide Gabriel M. Zimmerman, 30, prosecutors said.
Loughner also pleaded guilty to the attempted murders of federal employees and congressional aides Ronald S. Barber, 65, and Pamela K. Simon, 63, prosecutors said.
Barber, who won a special election to fill Giffords' seat after she resigned, also plans to attend the sentencing and will give a statement in court, his spokesman Mark Kimble said.
Loughner admitted causing the deaths of Christina-Taylor Green, 9; Dorothy "Dot" J. Morris, 76; Phyllis C. Schneck, 79; and Dorwan C. Stoddard, 76, prosecutors said.
Loughner admitted injuring with a Glock pistol 10 people participating at an activity provided by the U.S. government and creating a grave risk of death to 13 more people, prosecutors said.
Prosecutors agreed to the plea deal after taking into account Loughner's history of mental illness and the views of victims and their families. The judge in August ruled Loughner competent to stand trial.
Kelly said after the plea deal that he and his wife were satisfied with the agreement.
CNN's Dana Bash and Kevin Bohn contributed to this report.