The suspect in the US supermarket shooting that claimed 10 lives appeared in court for the first time and his defence lawyer asked for a mental health assessment “to address his mental illness”.

Kathryn Herold, the lawyer for suspect Ahmad Al Aliwi Alissa, provided no other details about what he might suffer from.

During the brief hearing, Alissa, charged in connection with the incident in Boulder Colorado, appeared in court wearing a mask.

He did not speak other than to say yes to a question from the judge and did not enter a plea to the charges.

Alissa, 21, remains held without bail on 10 charges of first-degree murder and a prosecutor said that authorities planned to file more charges.

A law enforcement official briefed on the shooting had previously said the suspect’s family told investigators they believed Alissa was suffering some type of mental illness, including delusions.

Relatives have described times when Alissa told them people were following or chasing him, which they said may have contributed to the violence, the official said.