PHOENIX (AP) -- Reaching a plea agreement for the suspect in the deadly Tucson, Ariz., mass shooting is just one step.

On Tuesday, defense attorneys and prosecutors will need to accomplish the next: persuade U.S. District Court Judge Larry A. Burns that Jared Lee Loughner, who has been forcibly medicated at a federal prison, is no longer mentally unfit for trial.

A court-appointed psychiatrist is expected to testify that Loughner is competent to enter a plea.

If Burns agrees that Loughner is competent, as legal experts expect, a formal change of plea hearing will follow. That's when those in the court will hear from the 23-year-old college dropout at length for the first time, as the judge questions him about the agreement and changing his plea to guilty.

Burns may ask Loughner to recite his actions in his own words, but either his lawyer or the federal prosecutor could just read the facts of the January 2011 shooting spree at a Tucson supermarket as then-Rep. Gabrielle Giffords held a meet-and-greet with constituents.

Either way, Loughner will be asked to admit that he shot and killed six people, including the top federal judge in Arizona, and wounded 13 others, including Giffords. He'll need to convince Burns he understands what is going on, what he's doing and what he did.

Loughner could break down, change his mind about pleading guilty or show so little understanding of what he's doing that Burns could change his mind about the competency and reject the plea, lawyers not involved in the case said Monday.

"The fact that there is this planned change of plea is no guarantee that it will go forward," said Paul Charlton, a former U.S. Attorney for Arizona. "There are any number of things that would happen that would either cause it to be removed from the calendar or not go forward at all."

Loughner was flown Monday from a medical facility in Missouri to Tucson, authorities said. Experts have concluded that Loughner suffers from schizophrenia, and prison officials have forcibly medicated him with psychotropic drugs for more than a year.

The plea agreement that is expected to be made public on Tuesday would see Loughner sentenced to life in prison, taking the possibility of the death penalty off the table in the federal case, a person familiar with the case told The Associated Press on Saturday. The person was not authorized to discuss the case publicly and spoke on condition of anonymity.

News of an agreement hasn't yet brought any negative reaction from victims' families, and some have said they support the government decision.

The top prosecutor in southern Arizona's Pima County said last year that she may file state charges in the case that could carry the death penalty. An official in the prosecutor's office, Amelia Craig Cramer, declined to comment, saying the office did not have an active prosecution against Loughner.

The decision to spare Loughner a federal death sentence makes sense, said Dale Baich, a federal public defender in Phoenix who handles capital case appeals and isn't involved in the case.

"As time went on and there were numerous evaluations, I think everybody had a better understanding of Mr. Loughner's mental illness." Baich said. He added: "It appears that he will need to be treated for the rest of his life in order to remain competent."


Associated Press writer Pete Yost in Washington and Barry Massey in Santa Fe, N.M., contributed to this report.