Mental health officials believe Loughner is now competent to understand the charges against him in the shooting which killed six people and injured 13 at an event held by the congresswoman in Tucson.
According to the LA Times terms of the plea arrangement remaine unclear whether or not Loughner would admit guilt to all of the charges in return for a lengthy prison sentence rather than face a potential death penalty verdict at trial.
At the hearing Tuesday morning in U.S. District Court in Tucson, psychiatric experts are scheduled to testify that they have concluded that despite swings in Loughner's mental capacity, at this time he comprehends what happened and the significance of the charges against him.
Many victims and family members from the Jan. 8, 2011, shooting are likely to attend the hearing in downtown Tucson, not far from the site of the attack.
Loughner's agreement to plead guilty would probably end more than a year and a half of psychiatric evaluations including periods in which he was medicated at a federal prison hospital.
The indictment said a search of Loughner's home turned up a letter hidden in a safe in which Giffords thanked him for attending an earlier Congress On Your Corner event. Also in the safe was an envelope with handwriting that said, "I planned ahead" and "My assassination" and Giffords' name, "along with what appears to be Loughner's signature," the indictment said.
Prosecutors pointed to that as evidence that Loughner coldly calculated the attack.
But soon after his arrest, the focus immediately turned to whether he was mentally fit to stand trial.
Friends said loughner had tried marijuana and used alcohol; while attending college, and he videotaped a rant in September 2010 on the campus in which he screamed that the school was not following the Constitution.
According to the indictment, Loughner purchased the Glock at a Tucson gun shop in November 2010 and the ammunition at a Wal-Mart store on the morning of the shooting. He took a taxi to the Safeway parking lot where Giffords was holding her constituent meeting.
Loughner was placed under suicide watch and often paced in circles about his cell, according to court records and pretrial testimony. He screamed and cried. He remained convinced that Giffords was dead, and became angry when told she survived. Once, advised he might face the death penalty, Loughner sobbed for nearly an hour. "I want to die," he said. "Give me the injection now. Kill me now."
According to court records, two medical experts agreed that Loughner suffered from schizophrenia and predicted that any improvements would be far away, if possible at all.
In a May 2011 hearing, federal marshals forcibly removed Loughner from the courtroom after he began shouting, something like "kill free" or "kill shot" — words that were hard to understand. Then he yelled, "She died in front of me!"
Given the option of behaving or watching the proceedings from a nearby cell with a remote television screen, Loughner chose the cell.