Dylann Roof, the 21-year-old man charged with murdering nine worshippers at a historic black church in Charleston last month, listens to the proceedings with assistant defense attorney William Maguire during a hearing at the Judicial Center in Charleston, South Carolina July 16, 2015. REUTERS/Randall Hill

(Reuters) – Attorneys for a white man accused of killing nine black parishioners in a racially motivated attack at a South Carolina church a year ago argued that their client should not face the death penalty, asserting the punishment is unconstitutional.

Federal prosecutors are seeking the death penalty against Dylann Roof, 22, who is accused of opening fire on a Bible study session at Charleston’s historic Emanuel African Methodist Episcopal Church on June 17, 2015.

The shooting shook the country and intensified debate over U.S. race relations, which were already roiled by numerous high-profile police killings of unarmed black people.

Attorneys for Roof argued in a document filed in a U.S. District Court in South Carolina on Monday that the federal death penalty is “cruel and unusual punishment” and, as a result, violates the U.S. Constitution.

“No one can be lawfully sentenced to death or executed under it, no matter what his crimes,” the attorneys wrote in the motion.

A court ruling that the Federal Death Penalty Act is unconstitutional would allow Roof to plead guilty and proceed to the sentencing phase of his case in which he could be to life in prison without parole, his attorneys said.

In an earlier court filing, federal prosecutors cited a number of factors for seeking the death penalty, saying Roof singled out victims who were black and elderly, and showed no remorse. They also cited “substantial planning and premeditation.”

The argument that the death penalty is unconstitutional is a typical line of defense. The federal trial against Roof is set to begin on Nov. 7.

Federal death sentences are rarely carried out in the United States. Roof also faces a state capital punishment trial, which is scheduled to begin in January.

Roof faces different charges in each case. State prosecutors in South Carolina charged him with murder and attempted murder, while federal prosecutors charged him with 33 counts including hate crimes, obstruction of religion and firearms offenses.

(Reporting by Brendan O’Brien in Milwaukee; Editing by Raissa Kasolowsky)