District of Columbia sniper John Allen Muhammad should not be executed because he suffers from mental illness and brain damage, his attorneys say.

Muhammad's defense team filed a brief with the U.S. Supreme Court saying their client was delusional and paranoid at his trial for a 2002 Washington area shooting spree, the Washington Post reported Wednesday.

Muhammad, 48, and Lee Boyd Malvo, now 24, were convicted in a series of random shootings that left 10 people dead.

In the Supreme Court brief, Muhammad's defense team says the attorneys who represented him at trial should have requested a competency evaluation.

"Trial counsel knew that Muhammad had been diagnosed with severe mental illness, and personally observed Muhammad's struggle with severe psychiatric disorders prior to the start of the trial," the team wrote.

Unless the Supreme Court or the Virginia governor intervenes, Muhammad is scheduled to die by lethal injection Nov. 10.