The suspect in the shooting of Rep. Gabrielle Giffords smiled and nodded but didn't speak as he appeared in court Monday and his lawyer provided the 22-year-old's first response to the charges: a plea of not guilty.

In the two weeks since the deadly attack that killed six outside a Tucson grocery store, Jared Loughner's hair — shaved in the mug shot that's become an enduring image of the tragedy — has grown out slightly. The Tucson resident wore an orange prison jumpsuit and glasses, and his wrists were cuffed to a chain around his waist as eight U.S. Marshals kept watch in the packed Phoenix courtroom and gallery above.

Loughner faces federal charges of trying to assassinate Giffords and kill two of her aides. More charges are expected.

Investigators have said Loughner was mentally disturbed and acting increasingly erratic in the weeks leading up to the attack on Jan. 8 that wounded 13. If Loughner's attorney uses mental competency questions as a defense and is successful, Loughner could be sent to a mental health facility instead of being sentenced to prison or death.

But his attorney, Judy Clarke, said she wasn't raising issues of competency "at this time" after U.S. District Judge Larry Burns of San Diego asked whether there was any question about her client's ability to understand the case against him.