On Day 24 of the Atlanta Public Schools cheating trial, Bob Wilson took the stand.

In all of the moments of the dramatic and gut-wrenching trial, which included sobbing witnesses, outbursts by lawyers and threats from the judge, his authoritative testimony that day may have had the biggest impact on the educators who stood accused.

A Southern gentleman familiar with the courtroom, he was one of the major characters in this tragedy — a player with insights that only one of the lead investigators could possibly have.

Wilson is a former DeKalb County District attorney, and he’s also been a public defender. He’s had a long career as a lawyer since graduating from Emory University’s law school in 1974, and he’s respected by friend and foe.

He was one of three investigators then-Gov. Sonny Perdue appointed in August of 2010 to investigate the accusations of cheating within APS.

From that moment, he dug into the matter with the determination and skill of a seasoned investigator. He told Perdue that the case would be difficult and complicated, and sought the governor’s assurance that the investigators would get the time and support to find the truth.

He’d worked on huge cases before, he said, and it would be hard.

He, with his partners Mike Bowers, the former attorney general, and Richard Hyde, set off down a road that would bring them face-to-face with the front-line educators who chose to betray the trust of the kids they stood in front of each day.

When I talked to him the day after the verdict, Wilson said one of the most memorable moments for him was his first meeting with APS Superintendent Beverly Hall. He was careful, respectful but pointed in recollection, and noted that because of her death, the trial lacked some important information.

First, the investigators talked to Hall’s senior team, who said, incredibly, they weren’t sure if her schedule would allow her time to talk to the investigators. And her team said they intended to do their own investigation. By then, several APS efforts to dig into questionable test scores had frustrated the governor and others, so Wilson told them that they would be interfering with a state investigation if they did so. They instead agreed to cooperate, although Wilson doesn’t give them high scores for their cooperation.

When the investigators finally talked to Hall, Wilson said he recognized, during that very first interview, that cheating was part of the APS culture. Why?

Hall told the investigators that she’d given principals a three-year deadline to meet testing standards of student proficiency. Hall’s standards were higher than the No Child Left Behind law required, she said.

The principals would either meet the standards or lose their jobs.

“Any time the head of an organization gives that kind of command, there is something wrong,” he said. “That edict from her became the driving force for all that followed.”

The investigators worked with the companies that created the tests, to replicate analysis of them and to understand how they were analyzed.

Wilson also recognized the work of The Atlanta Journal-Constitution on the cheating scandal. In fact, he tells people that the first thing the state investigators did was read the stories we’d published about the questionable test scores.

“As we went through the investigation, never one time do we find a fact reported by the AJC not to be correct,” Wilson said. “Not once do we find anything the AJC reported to be in error.”

The AJC faced a lot of criticism in the early days of the scandal, much of it from Hall. She criticized our reporting in a private meeting with me, as she urged me to drop the story.

My notes from that meeting reminded me that Hall blamed others for her difficulties, saying that the governor repeatedly took action without first informing her.

Wilson, because of his work on some high-profile cases, isn’t shy about criticizing the media when he feels we deserve it, so his endorsement of our reporting remains a point of pride in our newsroom.

In the end, Wilson dedicated himself to a year-long investigation he called “exhausting.”

About 80 people worked on the investigation, he said, including more than 50 Georgia Bureau of Investigation agents. They interviewed 2,000 people, some of them more than once.

And Wilson saw first-hand what Hall’s APS culture created.

As he testified that day in court: “In the end, I don’t think it had anything to do with children. It had to do with image.”

In our conversation after the trial, Wilson said he wasn’t surprised by the convictions based on a conspiracy.

“Concern for themselves outweighed their concern for children,” he said of the educators. “Some were determined to lie to the bitter end.”

Wilson has that quality that all the best investigators have: compassion, allowing him to draw out the truth under difficult circumstances.

“We also saw some good people who went along,” he said. “We watched them break down and cry. At least they told the truth.”

“It just breaks your heart.”

Wilson said the APS case changed him, giving him more admiration for good teachers and heightening his awareness of what it takes to educate disadvantaged children.

“It increased my respect for truly committed teachers,” he said. “We don’t pay teachers enough.”