The trial of the former school resource officer who remained outside a Parkland, Florida, high school five years ago while 17 people were gunned down inside is scheduled to begin in earnest Wednesday, as the jury hears prosecutors and defense attorneys give their opening statements.

The state has accused retired Broward Sheriff's Office Deputy Scot Peterson of failing to follow his active shooter training by staying outside Marjory Stoneman Douglas High School on February 14, 2018, taking cover for at least 45 minutes while a former student carried out what remains the deadliest high school shooting in US history. Among the slain were 14 students and three staff members; 17 others were injured.

The case highlights the expectations for officers responding to active shooters as the country faces a seemingly endless scourge of gun violence, with schools like those in Parkland; Uvalde, Texas; and Newtown, Connecticut, etched in public memory as the scenes of some of the most devastating massacres.

Peterson has pleaded not guilty to 11 counts -- including seven of felony child neglect, three of culpable negligence and one of perjury -- and maintains he did nothing wrong. The 60-year-old, who retired as criticism of his alleged failure mounted, has said he didn't enter the unfolding scene of carnage in the school's 1200 building because he couldn't tell where the gunshots were coming from.

Before the shooting, Peterson was a dedicated and decorated officer who had served for more than three decades, his attorney, Mark Eiglarsh, told CNN.

"After a 32-year career, this loving husband and father of four went from hero, and in 4 minutes and 15 seconds, he went to criminal," the defense lawyer said.

Jury selection began last Wednesday, yielding a panel of six jurors and four alternates tasked with weighing the state's unusual case, which experts have described to CNN as the first of its kind and a legal stretch.

The Broward State Attorney's Office charged Peterson under a Florida statute that usually applies to caretakers, arguing the then-deputy, in his capacity as a school resource officer, was a caregiver responsible for the protection of the high school's students and staff.

Peterson was at the school administration building on February 14, 2018, when the shooter opened fire on the first floor of the 1200 building, according to a probable cause affidavit. Peterson got to the building's east entrance about 2 minutes later, per a timeline in the affidavit.

Peterson moved about 75 feet away and "positioned himself behind the wall of the stairwell on the northeast corner of the 700 Building" -- a third campus structure -- the affidavit says, calling it a "position of cover" he held for the duration of the shooting.

In a blow to both the state and the defense, the judge last week ruled jurors will not make a trip to the scene of the shooting, as the jury in the shooter's trial did, CNN affiliate WPLG reported. Eiglarsh wanted the jury to see the exterior of the 1200 building, which has been preserved pending the trials of the shooter and Peterson, while prosecutors had wanted jurors to see the building's interior, too.

Beyond the child neglect and culpable negligence charges, Peterson was charged with perjury for telling investigators he heard only two or three gunshots after arriving at the scene of the shooting, the affidavit says, while other witnesses said they'd heard more.

Peterson's attorney intends to argue, in part, that his client's confusion about the location of the shooter was reasonable and shared by others at the scene, including members of law enforcement, teachers and students, Eiglarsh told CNN. The lawyer also contends Peterson's actions at the scene illustrate he was not negligent but reacting as well as he could with the information he had, he said.

Additionally, Eiglarsh disagrees with the decision to charge his client under the caretaker statute, he told CNN, calling the choice "preposterous."

"He's not a legal caregiver," Eiglarsh said, acknowledging he understands the argument. "But he's not a teacher, he's not a parent, he's not a kidnapper who's responsible for the well-being of a child. He's not hired by the school system."

In the past, Peterson and his attorneys have argued the caretaker statute does not apply to him, emphasizing one person is responsible for the deaths and injuries that day: the gunman, then-19-year-old Nikolas Cruz, who pleaded guilty to 17 counts of murder and 17 counts of attempted murder and was sentenced last year to life in prison without the possibility of parole after a jury declined to unanimously recommend the death penalty.

That outcome angered and disappointed many victims' families, including some who see Peterson's trial as another opportunity for justice.

"We should not portray or allow the defense team or the deputy who failed to act properly to portray himself as a victim," Tony Montalto, the father of 14-year-old victim Gina Montalto told CNN before jury selection. "He was charged with keeping the students and staff safe, and he failed to do so."

"Regardless of the outcome in the trial," he said, "I hope he's haunted every day by the fact that his actions cost lives."