Amanda Knox's former boyfriend Raffaele Sollecito took the stand in an Italian court Wednesday, defending himself at a retrial in the 2007 killing of British exchange student Meredith Kercher.

"I would like to make you understand that these charges against me are absurd," he said. "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," Sollecito said of what he's been through.

"Right now, I don't have a real life."

Sollecito, 29, is not testifying in the case, which is being heard in an appeals court in Florence. But he made a spontaneous declaration, which is the right of any defendant in an Italian trial, and he is not under oath.

He and Knox were convicted in 2009 of killing Kercher, 21, who was found stabbed in November 2007 in the villa that she and Knox rented in the central Italian university town of Perugia.

Their convictions were overturned in 2011 for "lack of evidence." But Italy's Supreme Court decided last year to retry the case, saying the jury that acquitted them didn't consider all the evidence and discrepancies in testimony needed to be answered.

Both Knox, 26, and Sollecito have maintained their innocence.

Afraid to return

The retrial began on September 30 without either of them present in court. The presiding judge, Alessandro Nencini, read out the details of the case, including the conviction of Ivory Coast citizen Rudy Guede for his role in Kercher's murder.

Knox returned to her hometown of Seattle after her acquittal and has been living there since. She says she is afraid to return to Italy, where she spent four years behind bars.

Sollecito was in the Dominican Republic at the start of the retrial but returned to Italy.

He and Knox made several spontaneous declarations throughout the original trial and first appeal. But only Knox testified.

DNA tests

The court hearing Wednesday is expected to address new DNA tests of the knife that prosecutors say was used to kill Kercher. The knife was a critical piece of evidence in the original trial.

The tests involve a small portion of the knife. According to recent Italian media reports, the tests rule out the possibility that Kercher's DNA is present in the sample. That would support Knox and Sollecito's case.

The results are expected to be revealed in court Wednesday. Written conclusions by forensic experts have already been filed in Florence.

The Italian authorities who examined the spot on the knife are expected to present their report. They will then be questioned by all parties.

Knox isn't the only person watching the retrial from afar.

Citing health reasons, Kercher's relatives said in September that they had decided not to return to Italy for the retrial. The family said it would follow closely from Britain and remain in close contact with lawyers.

CNN's Hada Messia contributed to this report.