Houston, Feb 13: The suspect accused of killing 22 people in a mass shooting at a Walmart in El Paso, Texas, last year, has pleaded "not guilty" to 90 charges, among them hate crimes and murder.

On Wednesday, Patrick Crusius, 21, appeared before magistrate judge Miguel Torres in the El Paso federal court, where federal charges against him over the August 3, 2019 incident were formally read, reports Efe news.

"We are going to do everything in our power to preserve, protect and defend the Constitution of the United States of America," David Lane, Crusius' defence attorney told reporters.

Crusius, who didn't speak, refused to listen to the 90 counts - 22 of using a firearm to commit murder, 22 of committing hate crimes resulting in death, 23 of using a firearm in a crime and 23 of committing a hate crime with intention to kill.

He then pleaded "not guilty" in writing.

Prior to the charge reading hearing, the defence had requested that Crusius, originally from Allen, Texas, appear unrestrained and without a uniform.

The judge only allowed him to shave and dress in a suit but insisted that his hands and feet be cuffed in a session that allowed no access to cameras or microphones, but did allow relatives of the victims because it was a federal case.

"The Court finds it appropriate that the Defendant be restrained at his initial appearance ... using the customary restraints used by the US Marshals under the circumstances," Torres wrote in an order prior to Crusius' court appearance, adding that he posed a security risk.

The next hearing is scheduled for February 18, but Lane said he would look for a way for neither him nor his client to appear.

Crusius had already pleaded "not guilty" in October 2019 over homicide state charges in connection with the killing.

The alleged perpetrator of the shooting, in which 22 people died and 25 others were injured, confessed to police when arrested that his goal was to kill as many Mexicans as he could. Of those killed in the incident, eight were Mexican citizens.

Crusius told police that it was he who opened fire on a crowd at a Walmart shopping centre in the border city where many Mexicans often come to shop.

Suspect of 2019 Texas mass shooting pleads 'not guilty'