CHICAGO (CBS) — On Sept. 23, 2015, Mario Casciaro was surrounded by relatives as he left Menard State Prison – having been exonerated of orchestrating a murder 13 years earlier in the northwest suburbs in which the body was never found.

The case took a number of twists and turns since the man he was accused of having killed, Brian Carrick, was last seen on Dec. 20, 2002.

Carrick was 17 years old at the time. He and Casciaro both worked at a grocery store co-owned by Casciaro’s family in far northwest suburban Johnsburg.

Carrick was a stock boy at the store, while Casciaro was his supervisor. Prosecutors claimed Casciaro hired another co-worker to kill Carrick over a drug debt.

While Carrick’s body was never found, prosecutors said his blood was found in a cooler and a trash compactor inside the store.

Published reports said in 2007, Casciaro was charged with perjury with regard to his grand jury testimony about Carrick’s disappearance. Prosecutors claimed that Casciaro denied knowing that he knew how Carrick was killed and what happened to his body, reports said.

Casciaro was tried on those charges in 2009, but during the trial, a judge tossed the charges on the grounds that prosecutors had not proven their case, published reports said.

But the following February, Casciaro was charged directly in Carrick’s murder. He went on trial on the new charges in January of 2012.

At trial, prosecutors claimed that Carrick dealt drugs for Casciaro and owed him money. Prosecutors claimed on the day Carrick had last been seen, Casciaro had a friend, Shane Lamb, try to collect the money from Carrick.

Lamb testified against Casciaro with a grant of immunity from prosecutors. He testified that he lost his temper with Carrick and punched him, knocking him out. But he said Casciaro told him to leave after the fight and that he didn’t know what happened to Carrick after that.

Prosecutors argued that Casciaro wasn’t the one who delivered the fatal blows, he was responsible for setting Carrick’s murder in motion.

But the jury was not convinced. The trial ended in a hung jury in Feb. 1, 2012, after jurors deliberated for about 12 hours over two days.

In March 2013, Casciaro was put on trial again on the same charges. On April 2 of that year, a jury convicted Casciaro.

His family was furious.

“It’s not fair what they’re doing,” his mother, Maria Casciaro, told CBS 2’s Brad Edwards that day. “Mario – he never did anything. He was very honest all the time. And then look what they did.”

Casciaro’s family’s outraged intensified as he was sentenced to 26 years in prison on Nov. 14, 2013. His family walked out of court in stunned silence, holding protest signs.

“He shouldn’t have even gotten one year,” Casciaro’s sister, Julie, said that day. “He’s innocent.”

“There was no physical evidence, no DNA, no witnesses, and no motive,” added Casciaro’s sister Joanne.

Carrick’s father, William, believed Casciaro was guilty and said Casciaro had “earned his place” in prison. But his family hired attorney Kathleen Zellner to appeal – and the key witness recanted his testimony and said he lied under oath.

And in September 2015, the Illinois Appellate Court overturned Casciaro’s conviction.

The Appellate Court ruled that “the state’s evidence was so unreasonable, improbable and unsatisfactory that a reasonable doubt exists.”

Six days later, Casciaro was released. The day after that, he talked with the late CBS 2 reporter Mike Parker about his ordeal.

“I am not an angry person,” Casciaro said. “I just want to prevent this from happening to the next person.”

He said he wanted prosecutors to be held accountable for cases like his.

“A prosecutor can frame somebody that he just happens not to like. There’s no problem with it,” Casciaro said in 2015. “Not a slap on the wrist, he just moves on to the next guy.”

He also said he still wondered what really became of Carrick.

“All the time, it’s one of those questions that you’re saving to ask God, other than what’s the meaning of life,” Casciaro said at the time.

Casciaro added that he wanted to become a lawyer and get into politics. And just this past Tuesday, Casciaro, now 36, got word that he had passed the Illinois Bar Exam.

His attorney Kathleen Zellner tweeted this past Tuesday: “Just heard that my client Mario Casciaro passed the Illinois Bar exam. He will be a great lawyer who truly understands the plight of the wrongfully convicted.”

TONIGHT AT 10: CBS 2’s Charlie De Mar’s interview with Mario Casciaro about the start of the newest chapter in his life.