What the plea didn’t make easier was his sentence. In Florida, first degree murder is a felony punishable by either death or life in prison without the possibility of parole. And state law requires a jury to determine who it should be. If defendant had been convicted at trial, the same sentencing court would have been retained for a separate sentencing proceeding. But when a defendant pleads guilty before a felony trial, as Mr. Cruz did, the court must empanel a jury only for sentencing unless the defendant waives the right to ask the jury to decide .

What the state does

The prosecution’s job now is to convince the jury that there are aggravating factors in the case that would warrant the death penalty. Among the potential aggravating factors listed in the law are:

That the killings were “particularly heinous, horrific or cruel”. That the defendant “knowingly created a great risk of death to many persons.” That the defendant killed “in a cold, calculated and premeditated manner without any pretense of moral or legal justification.”

Prosecutors are expected to present extensive details of the 17 murders and 17 attempted murders at the high school, including hundreds of gruesome photos and videos. The jury can also tour the school building where the shooting took place. “They’re going to try to get these jurors to relive what happened to the victims,” ​​said David S. Weinstein, a former prosecutor who is now a defense attorney. “It’s going to be an emotional roller coaster.”

What does the defense do?

The defense will try to convince the jury that there are mitigating circumstances that warrant leniency. Under the law, those circumstances could include that the defendant “was under the influence of extreme mental or emotional disturbance” or had an impaired ability to understand whether his actions were criminal, among other factors. Defense lawyers plan to show that Mr. Cruz, who was 19 at the time of the shooting, had a difficult upbringing and mental health issues and had tried to get treatment. They asked for permission to show jurors a map of his brain, but the judge has yet to decide whether to allow it.

Jury work

After hearing the evidence, the jury must first decide whether the State has proven each of the alleged aggravating factors beyond a reasonable doubt. For a defendant to be eligible for the death penalty, the jury must unanimously find at least one of the aggravating factors to be proven. The jury will then consider whether the proven aggravating circumstances are sufficient to warrant a death sentence and outweigh the mitigating factors found to exist, and, if so, whether to recommend the death penalty to the jury. To do this, the jury must again be unanimous. Otherwise, the recommended sentence must be life imprisonment without the possibility of parole. The court cannot impose the death penalty if the jury has recommended life imprisonment, but it can overturn the jury’s recommendation of death and impose a life sentence.

Strange case

The need for a special jury is one of the many ways in which the Parkland case is highly unusual. It is rare for someone as young as Mr. Cruz (now 23) to face the death penalty, and even rarer for someone who has committed such a deadly mass shooting to still be alive afterward to face justice. “In a sense, we’re in completely uncharted waters,” said Robert M. Jarvis, a law professor at Nova Southeastern University in Davie, Florida, who tracks mass killings. “You never have these kinds of trials, because the gunman is always dead.” Patricia Mazzei contributed reporting.