Luciano Aviello, a transgender ex-member of the Camorra crime family who now goes by the name Luciano Lucia, met Knox's former Italian lover Raffaele Sollecito while the two were in prison following the original 2009 conviction, Skynet News said Saturday.
Knox and Sollecito are accused of sexually assaulting and killing Kercher, Knox's British roommate, in 2007.
The two were convicted in 2007 but the conviction was overturned on appeal in 2009. Then, in 2011, Italy's highest court ordered a retrial.
Neither Knox nor Sollecito has attended the retrial. Knox returned to her native Seattle after she was released following her appeal. Sollecito has not attended the trial yet but his lawyer said he plans to make a "voluntary statement" at some point, ANSA News Agency said.
Aviello, whose testimony was tossed in a previous trial and who was charged with perjury, said it was actually her brother, Antonio, also a member of the Italian underworld, who broke into the roommates' house in a random robbery attempt and killed Kercher.