GEOFF BENNETT: The 2018 massacre at the Tree of Life Synagogue in Pittsburgh that killed 11 people is considered to be the deadliest attack on Jews in U.S. history.

A federal jury convicted the gunman of 63 charges, including 11 counts of hate crimes.

And, as John Yang reports, the same jury is now deciding whether to recommend the death penalty.

JOHN YANG: Geoff, this phase of the trial is really what the case has been all about.

Defense lawyers readily acknowledged during the guilt phase that the gunman planned and carried out the attack.

The jury is now in the third day of hearing from the victims' families and friends.

Later, the defense will make its case for a sentence of life in prison.

This phase of the trial is expected to take at least a week.

David Harris is a law professor at the University of Pittsburgh Law School.

He's also an adviser to the 10.27 Healing Partnership, which is a consortium helping the victims, survivors and broader community deal with the shooting and its aftermath.

To get to this phase, Mr. Harris, they had to go through a phase where they determined that the shooter was eligible for the death penalty.

Now they're deciding whether or not to recommend the death penalty.

Does the law give them any -- say anything about what factors they ought to be considering in making this decision?

DAVID HARRIS, University of Pittsburgh: Yes, it does, John.

And it's very clear about this.

At this phase, the penalty phase, the jury is to consider evidence of aggravating factors and mitigating factors.

Aggravating factors are things that would push the jury toward a sentence of death.

And they can be things like a killing that is particularly heinous, victims who are particularly vulnerable, multiple victims.

All of this is spelled out in the law, the statutes that cover the death penalty and also by court decisions.

This is balanced, then, against mitigating factors coming from the defense.

And the defense mitigating factors could be things like brain trauma, mental illness, adverse childhood events.

All of that will be weighed and balanced by the jury.

And from that weighing and balancing, they will make the determination of whether this defendant is sentenced to death or life without parole.

JOHN YANG: And what the prosecution is doing now, putting up essentially victim-impact statements... DAVID HARRIS: Yes.

JOHN YANG: ... we have heard widows talk about losing their husbands, grandchildren talk about losing their grandmother, even the girlfriend of one of the police officers who was wounded talking about what that wound has done to his life.

Is this all in trying to convince the jury that it is worth the death penalty?

DAVID HARRIS: Yes, that's what it is.

This is the prosecution's aggravating evidence.

And nothing is typically more powerful than testimony from people who were victimized themselves or whose loved ones were the subject of the murder.

That's what we have here.

The Supreme Court allows this kind of victim-impact evidence at this stage to show the jury a kind of slice of life.

What has it meant that this victim has been lost?

What has it meant to the families, to the workplace, to the community at large?

And the court says that the jury can weigh this as part of the aggravating factors.

It is typically very, very impactful.

JOHN YANG: And based on what we have heard in the guilt phase of this trial and also in the phase to determine whether he was eligible, what do we expect the defense, what mitigating factors do we expect the defense to present?

DAVID HARRIS: The defense has treated the entire case front to back as a preview so far of its mitigating evidence.

So we know pretty much what they're going to bring.

What we will hear about is the fact that they say that the defendant has a series of mental illnesses, that perhaps he has schizophrenia, that he has epilepsy and other mental disease, that he had some very terrible things happen during his childhood.

As they said in their opening argument for this phase of the trial, don't add more death to this, punishment, yes, death, no.

JOHN YANG: And on that point, I know that you live in -- fairly close, relatively close to the synagogue where this shooting took place.

It's a very tight-knit community, still very much a Jewish enclave.

And I know that there is an array of opinions about whether this man should get life or get the death penalty.

What do you hear from your neighbors, what do you hear from your fellow congregants to sort of illustrate this?

DAVID HARRIS: Well, this is the most common question I get asked, as a person who taught classes to help the community come to grips with the trial.

And we're a mixed group of opinions, just like Americans are, on the death penalty.

There are many people who say, if this isn't a death penalty case, I don't know what it is.

If anybody ever deserved the death penalty, this guy does.

Others are just as opposed to the death penalty under any circumstances, even these.

So there is not a unanimity of opinion on this.

What we are is united in our determination to support the victims, to see the process through correctly, to see the best we can as human beings that justice is done.

We don't always get what we want out of the legal process.

But what we will get here is, we will know that this case was carried out consistent with our values as a community, whether our values as a Jewish community, an American community, the community of Pittsburgh.

That's what we have going for us.

But what we're seeing here is a city and a community coming to grips with the worst thing that can happen in very solid way that seeks justice.

JOHN YANG: David Harris from the University of Pittsburgh Law School, thank you very much.

DAVID HARRIS: My pleasure.