The jury for Pittsburgh synagogue mass shooter has begun deliberations to decide if the death penalty phase of the trial should continue

The jury in the trial of the Pittsburgh synagogue mass shooter began deliberating Wednesday about whether he is eligible for the death penalty.

If the jury finds he is eligible, they will move to a final phase of the trial, called sentencing selection, to consider whether to recommend the death penalty for the capital offenses in light of all aggravating and mitigating factors.

This final phase is expected to last several weeks.

The jury can also decide Bowers is ineligible for the death penalty at this stage, ending their deliberations and resulting in life sentences for the capital counts.

Robert Bowers, 50, was found guilty on June 16 of all 63 charges against him for killing 11 worshipers and wounding six others at Pittsburgh's Tree of Life synagogue in 2018, the deadliest attack on Jewish people in the US. Twenty-two of those counts were capital offenses.

The jury deliberated for about an hour. Deliberations resume Thursday morning.

The death penalty trial is split into two parts, the guilt phase followed by the penalty phase. In this case, however, the judge granted the defense's request to split the trial into three parts: the guilt phase, the eligibility phase and the sentencing selection phase. Each part has opening statements, closing arguments and a verdict.

During this eligibility phase, prosecutors had to prove Bowers had an intentional mental state when he committed the crimes and at least one aggravating factor applied to the mass shooting. They argued the shooting showed extensive planning and clear intent that, in Bowers' own words, "All Jews had to die."

In contrast, the defense sought to question whether Bowers acted with intent and highlighted his mental health issues. Several doctors testified they diagnosed him with schizophrenia and noted his delusional thoughts and conspiracies about Jews.

During closing arguments Wednesday, the defense team said the shooter's delusions "took over his thinking."

"In 2018, that delusional belief system took over his thinking and made him incapable of really doing anything except following the dictates of that belief system," defense attorney Michael Burt told the jury.

The defense team has focused on the threshold intent factors in the case, attempting to prove that Bowers was incapable of forming the intent to kill or inflict serious harm due to mental illness, which Burt emphasized in his 90-minute closing argument.

"People don't go into a church and kill a bunch of older people for no reason," Burt said. "We've tried to provide you with reasons that we think explain how this horrible crime could've happened."

Two medical experts called by the defense testified the shooter diagnosed Bowers with schizophrenia, and one diagnosed him with epilepsy. Other experts testified that Bowers has shown signs of these conditions, as well as delusions.

Burt said there's a difference between "a rational, conscious intent to kill, as opposed to a crazy, delusional intent that is found in mental illness."

In the prosecution's rebuttal argument, attorney Eric Olshan disputed the defense experts' diagnoses, saying Bowers does not have schizophrenia, epilepsy, or delusions.

"He just believes things that are repugnant," Olshan said.

"Even if the defendant had these illnesses, they would say nothing about whether he could form the intent to kill," the prosecutor told the jury.

"Don't be distracted from the simple and commonsense fact that everything the defendant did in the months leading up to October 27 and on that horrific day was because that's exactly what he intended to do," Olshan said.

US District Judge Robert Colville instructed jurors before closing arguments, asking them not to consider the fact that Bowers did not testify in the trial. "You must not draw any adverse inference against him because he did not take the witness stand," he said.

The jury heard from a total of 20 witnesses over more than two weeks of testimony in the trial's latest phase.

In 2018, Bowers approached the synagogue with three handguns and an AR-15 rifle and began firing near the entrance to the synagogue and then opened fire on congregants, according to testimony.

Police eventually shot Bowers multiple times before he surrendered and was arrested.

Those who died included a 97-year-old great-grandmother, an 87-year-old accountant and a couple married at the synagogue more than 60 years earlier.

CNN's Laura Dolan and Ray Sanchez contributed to this report.