Pasadena, California (CNN) -- The medication Jared Loughner is receiving to make him competent to stand trial could prevent that trial from being fair, an attorney for the alleged Tucson shooter told a federal appeals court Tuesday.
The side effects of the psychotropic drugs he has been receiving during his court-ordered treatment may interfere with Loughner's ability to work with his attorneys, said defense attorney Ellis Johnston.
"What is the effect of the drugs on the likelihood of achieving a fair trial? That is what the court has to address," Johnston said during the hearing before the U.S. Ninth Circuit Court of Appeals in San Francisco.
Senior Circuit Judge J. Clifford Wallace asked Johnston whether the court shouldn't wait for Loughner to complete his four months of treatments before considering whether the drug therapy is hindering Loughner's ability to work with his attorneys.
Johnston replied that the U.S. Supreme Court required the courts to consider whether the drugs could create a substantial chance that Loughner won't have a fair trial.
Johnston also argued that the antipsychotic drugs, while they may be treating Loughner's psychosis, are not making him "less dangerous, and they may be exacerbating his dangerousness."
Loughner's attorneys are appealing a lower court's order for a second four-month course of treatment at a federal mental hospital in Springfield, Missouri. That court ruled the extension was necessary to make Loughner competent to stand trial in the killing of Arizona's chief federal judge, John Roll, and the wounding of U.S. Rep. Gabrielle Giffords, D-Arizona.
Loughner, 23, is accused of killing six and wounded 13 in January during a meet-and-greet event for Giffords outside a Tucson, Arizona, shopping center.
Last month, the Ninth Circuit denied a temporary request to stay Loughner's transfer back to the hospital.
Loughner suffers schizophrenia, prosecutors said.
In July, bizarre and suicidal actions by Loughner while in custody pushed the federal appeals panel to allow authorities to force the defendant to take the anti-psychotic medication.
Prosecutors said in July that Loughner had been deteriorating: He displayed screaming and crying fits that lasted hours, harmed himself, and made claims that the radio was inserting thoughts into his head, they said.
On Tuesday, Johnston told the court that the drugs could have the side effect of creating a flat affect in Loughner's expression, hurting the defendant's right to a fair trial.
"It's even worse if the side effects of those drugs will prohibit him from expressing himself appropriately at trial," Johnston said.
But Assistant U.S. Attorney Christina Cabanillas said that Loughner "could revert to being a danger to himself" if the medication were halted.
"It is his mental illness that is the cause of the danger in the hospital setting," Cabanillas told the court.
Judge Wallace asked the prosecution about a possible scenario in which the antipsychotic drugs were successful in making Loughner competent for trial, in which Loughner would know the difference between right and wrong.
But, Wallace continued, if the medication had the side effect of interfering Loughner's ability to assist his lawyers in his defense -- violating due process -- could the government bring Loughner to trial?
Cabanillas said she needed to research that matter. "I need to check the law," she said.
While the case was being heard in San Francisco, it was delivered live by closed-circuit television to other federal appeals courts, including one in Pasadena.