© EPAJared Lee Loughner, Greenbaumed?
Witnesses reported Loughner smiled broadly throughout the hearing, including moment when his lawyer entered plea of not guilty

Jared Loughner, the suspect in the shooting of Democratic congresswoman Gabrielle Giffords, pleaded not guilty in court, in his first response to the charges.

Silent but displaying the grin that has become his trademark, Loughner made his second appearance in public since the attacks on 8 January at the federal courthouse in Phoenix, Arizona.

He is alleged to have killed six people and injured a further 13, including Giffords, during a deadly shooting rampage at a public meeting at a supermarket car park in Tucson.

Witnesses inside the courtroom reported that Loughner - shackled and dressed in an orange jump suit - smiled broadly throughout the hearing, including the moment when his lawyer entered his plea of not guilty.

Nicholas Riccardi, a journalist for the Los Angeles Times, said the 22-year-old "continued to flash an uncanny, self-satisfied grin throughout the otherwise routine nine-minute arraignment".

Loughner was surrounded by heavily armed marshalls on his journey to and from the courtroom. He faces five federal charges, including one of attempted assassination of a member of Congress, two charges of killing an employee of the US and two charges of intent to kill employees of the US. He will almost certainly receive Arizona state charges as well, and is likely to face the death penalty if convicted.

Loughner's lawyers gave no hint how they planned to defend him against the charges. When Judge Larry Burns asked if there were any doubts about Loughner's ability to understand the charges, his lawyer Judy Clarke said: "We are not raising any issues at this time."

Clarke is a veteran of several high-profile murder cases, having defended the Unabomber, Theodore Kaczynski, and the Atlanta Olympics bomber, Eric Rudolph, both of whom were convicted but escaped the death sentence.

Judge Burns is normally based in San Diego but Arizona's judges have all recused themselves from hearing the case since one of the murder victims was Arizona federal judge John Roll.

After the hearing prosecutors said they had passed on to defence lawyers copies of 45 disks-worth of material taken from Loughner's computer.

Loughner's next court appearance is on 9 March, when the full extent of charges against him will be revealed.