Italian Raffaele Sollecito was convicted of murder along with Knox at a retrial last month in the 2007 stabbing death of Meredith Kercher, in a decision that reversed an earlier appeal judgment that cleared the pair. The case is expected to conclude next year before Italy's highest court.
"It's imperative that the Italian courts consider Raffaele's case separate from Amanda's case," his attorney, John Q. Kelly, said in a statement.
"By necessity, he has to distance himself and his case from Amanda and her case. The facts and the evidence with regard to each of them is entirely different," said Kelly, who acts as Sollecito's spokesman in the United States.
Kercher, 21, was found stabbed to death in her bedroom in the apartment she shared with Knox in Perugia. Investigators initially built a narrative that Knox and Sollecito killed Kercher in a sex game gone awry, but the prosecution moved away from this interpretation in the latest retrial, which focused on a re-examination of DNA evidence.
Ivory Coast-born Rudy Guede is serving a 16-year sentence after he was found guilty of killing Kercher, but judges have ruled he did not act alone.
Commonly viewed as a villain in Italy, Knox is widely seen in the United States as the victim of a faulty justice system. Views in Kercher's country, Britain, are mixed and her family has said they may never know the truth about her death.
Knox returned to the United States in 2011 after spending four years in an Italian jail, and has vowed to fight any attempt to extradite her. Sollecito remains in Italy where he is free pending an appeal but is barred from leaving the country.
Kelly could not immediately provide additional comment.
Knox, 26, maintains she spent the night of Kercher's murder with Sollecito in his apartment. Sollecito, in a Feb. 3 interview with CNN, denied that evidence ties him to the murder of Kercher.
"There's nothing against me and nothing very strong against Amanda, and in my case I really did nothing wrong and I don't want to pay for someone else's peculiar behavior," Sollecito said in the interview with CNN.
Sollecito, in a 2012 memoir, wrote that members of his own family questioned Knox's account that when she returned home after Kercher's murder and discovered blood in the bathroom, she went ahead and took a shower anyway. Knox says she only discovered later that Kercher had been killed at the apartment.
The defense and prosecution contest whether Kercher's DNA was on the blade of a kitchen knife from Sollecito's apartment, which had been used by Knox.
In a Feb. 11 post on her blog, Knox said she had recently been exchanging emails with Sollecito, who had conveyed frustration about the case. She expressed sympathy for the Italian.
"As tenuous as the case is against me, it is illogical and unfair that Raffaele should be held legally answerable for it," Knox wrote in the blog post earlier this month.
A spokesman for Knox declined to provide additional comment.