The man accused of killing 11 worshippers at a Pittsburgh synagogue five years ago in the deadliest antisemitic attack in U.S. history could face the death penalty if found guilty in a federal trial that opened on Tuesday.

Robert Bowers, 50, is on trial on dozens of federal charges, including 11 counts of hate crimes resulting in death, over the mass shooting that unfolded at Pittsburgh's Tree of Life synagogue on Oct. 27, 2018. He has pleaded not guilty.

On Tuesday morning, federal prosecutors and attorneys for Bowers were scheduled to deliver opening statements to jurors. The trial, at the U.S. District Court in the western Pennsylvania city, is expected to take weeks to complete.

If jurors find Bowers guilty in the first phase of the trial, they will then determine whether he spends the rest of his life in prison or be executed by lethal injection.

In seeking the death penalty, federal prosecutors will try to show that aggravating factors were involved, making a case that Bowers carefully planned the attack and that he targeted vulnerable victims. Most of the victims were elderly.

In court filings, lawyers for Bowers have repeatedly tried to get the court to strike the death penalty as a sentencing option, calling it unconstitutional on the grounds that he suffers from major mental illness, including schizophrenia.

A one-time truck driver who frequently posted antisemitic slurs online, Bowers stormed the synagogue during Saturday services and yelled "All Jews must die," according to prosecutors.

In addition to the deceased, two other worshippers were wounded, along with five police officers. Bowers surrendered and was taken into custody after he was wounded in a shootout with police.

Bowers was carrying multiple firearms when he entered the synagogue in the city’s Squirrel Hill neighborhood, where many residents are Jewish, federal authorities have said.

(Reporting by Brendan O'Brien in Chicago; Editing by Conor Humphries)