Rome (CNN) -- Raffaele Sollecito was a 23-year-old computer science student when his girlfriend's roommate, Meredith Kercher, was found dead in the house she shared with Amanda Knox in Perugia, Italy, in 2007.
The discovery was the beginning of what Sollecito has called "a nightmare" he wouldn't wish on anyone.
In 2009, he and Knox were convicted of Kercher's murder. In 2011, the pair were acquitted -- only to have that decision overturned by Italian Supreme Court judges two years later. A retrial began in Florence in September 2013.
The initial guilty verdict at the 2009 trial had not been the result Sollecito had been expecting.
"When the sentencing was read, I didn't understand what was happening and even now it seems impossible and still I don't understand why I was convicted," he said in a prison interview through his lawyer the week after the sentencing. He said then he dreamed of returning to his studies.
Sollecito is from Bari, on the Adriatic coast, far south of the central Italian university town where he was studying. In his prison interview, he said he missed the smell of the sea, among other things.
"Above all my family," he said in the interview conducted via attorney Luca Maori. "I also miss my friends, the everyday life, the walks in my town's square."
Sollecito finished his computer science degree while in prison, according to media reports. He was not studying at the same university as Knox, and was not held in the same prison.
In the prison interview, he described how the verdict brought the world collapsing down on him and Knox.
But he denied then that he was still in love with her, saying, "I feel close to her because I consider her my companion in misadventure."
He rejected the idea that Knox was capable of murder. "I don't even dare think a thing like that. It is absurd and inadmissible. She is a very sweet girl," he insisted.
When their successful appeal saw Knox and Sollecito freed in 2011 -- after four years in prison -- they set about trying to rebuild their lives, a continent apart.
Sollecito had hoped simply to blend in in his hometown of Bari.
"I only hope to be forgotten; the sooner the better. I want to have a normal life," he said before his release. "I don't want to be recognized when I leave the prison."
'Journey to hell'
Sollecito published a book in 2012, the first by someone directly involved in the chain of events sparked by the discovery of Kercher's body.
The memoir, "Honor Bound: My Journey to Hell and Back with Amanda Knox," draws heavily on diaries he kept and letters he wrote to friends, family and his hometown newspaper during his years in prison, the preface says.
Sollecito chronicles the day of the murder, admitting that he and Knox smoked marijuana that afternoon, which he says he regretted because it clouded his memory of what happened. While maintaining his innocence, he says he does not clearly remember even if Knox spent the night with him.
He and Knox made mistakes the morning of the discovery, including trusting police investigators, he writes.
Sollecito acknowledges that at times, he was uncomfortable with Knox's "bizarre behavior," which he says prosecutors used against both of them.
In the epilogue, he recounts how he went to visit Knox in Seattle after their release, but he was nervous to see her. "I wasn't at all sure it was a good idea and I continued to waver back and forth even after I booked my ticket.
"We had been through so much; perhaps we owed it to each other to live our lives and leave each other in peace."
Rather than that hoped-for peace, Sollecito's nightmare began again following the 2013 ruling of the Supreme Court judges in Rome that there should be a retrial.
In an interview with CNN soon after the retrial opened in September 2013, Sollecito maintained his innocence.
"I just think that in the Italian system, there's something really wrong in the rules that they sometimes are not respected or they are turned to hurt people. And they can hurt actually innocent people," he said. "My life now is a hell."
Sollecito took the stand to defend himself in November.
"I would like to make you understand that these charges against me are absurd," he told the court.
"There was not a basis to charge me, to put me in jail ... I don't wish anybody on Earth to go through what I went through."
He said that evidence against him -- a knife that was a key part of the prosecution's case -- was "an illusion."
"I ask you ... to really look at reality," he implored the judges. "For me, it's a nightmare that goes beyond imagination ...
"Right now, I don't have a real life."
CNN's Barbie Natza Ladeau reported from Rome. CNN's Laura Smith-Spark and Richard Allen Greene reported and wrote from London. CNN's Hada Messia also contributed to this report, from Rome.