The sentencing hearing comes a day after a jury unanimously voted for the death penalty after finding Bowers guilty on 63 counts, including 11 counts of obstruction of free exercise of religious beliefs resulting in death.

Relatives of Bowers’ victims are expected to address judge Robert Colville during the hearing at the US district court in Pittsburgh in western Pennsylvania. The judge is required to hand down the sentence voted for by the jury.

During the trial, defence lawyers did not dispute that Bowers planned and carried out the attack on the synagogue during Sabbath morning services, in which he combed through the building shooting everyone he found with a semi-automatic rifle and three pistols.

Bowers’ lawyers unsuccessfully argued that he suffered from lifelong mental illness and was delusional, so the jury should spare him from the death penalty and instead sentence him to life in prison without release.

The 12 jurors heard testimony from some of the survivors of the attack and were shown pictures of the carnage and evidence of Bowers’ antisemitism, including multiple posts attacking Jews made on a far-right website in the months leading up to the attack.

It is not clear when, if ever, Bowers will be executed: the US Department of Justice has instated a moratorium on carrying out federal executions while it reviews the death penalty, which President Joe Biden pledged to abolish when he was running for the presidency.

Bowers will join the 41 other men on federal death row, held in cells near the US government’s execution chamber in Terre Haute, Indiana.