A court-appointed psychiatrist is to say Jared Loughner is competent to enter a plea over the shooting rampage that killed six people and injured 13 others, including then-US congresswoman Gabrielle Giffords, a person familiar with the case said.
The source said the plan was for Loughner, 23, to enter a guilty plea for the murders and attempted murders in Arizona that would result in a sentence of life imprisonment.
A status conference in the case had already been scheduled for Tuesday in Tucson. The plan is contingent on the judge in the case allowing Loughner to enter the plea.
Loughner pleaded not guilty to 49 charges stemming from the shootings on January 8 last year outside a Tucson supermarket where Ms Giffords was holding a meet-and-greet surgery with her constituents.
Authorities said he shot Ms Giffords and opened fire on the crowd until he was subdued by bystanders. Ms Giffords was shot in the head and subsequently left congress to devote her time to rehabilitation.
An Arizona college that Loughner attended released numerous emails about him that painted a picture of a struggling student with emotional problems who disturbed others with his strange behaviour.
US District Judge Larry Burns had ruled that Loughner was not psychologically fit to stand trial, but could eventually be made ready after treatment. Experts have concluded that Loughner suffers from schizophrenia.
Prison authorities in Missouri, where Loughner has been held, have forcibly medicated him with psychotropic drugs to make him fit to stand trial. Even though psychologists have said Loughner's condition is improving, his lawyers have vigorously fought the government's efforts to medicate him.
At one point, a federal appeals court halted the forced medication, but resumed it once mental health experts at the prison concluded that Loughner's condition was deteriorating further.
Loughner has demonstrated bizarre behaviour since his arrest. He was removed from a May 25 2011 court hearing when he lowered his head to within inches of the courtroom table, then lifted his head and began a loud and angry rant. His psychologist has said that since Loughner has been forcibly medicated, his condition has improved. He sat still and expressionless for seven hours at a hearing last September.