Aviello says his brother told him he killed Meredith Kercher in botched robbery . Amanda Knox 's says he buried brother 's bloody knife , clothes and keys to Kercher 's apartment . Amanda Knox 's lawyers want Aviello 's story investigated for her appeal . Meredith , her former boyfriend were convicted of murdering Amanda Knox 's in age 17 .
Luciano Aviello says his brother told him he killed Meredith Kercher in botched robbery . Aviello says he buried brother 's bloody knife , clothes and keys to Kercher 's apartment . Amanda Knox 's lawyers want Aviello 's story investigated for her appeal . Knox , her former boyfriend were convicted of murdering Kercher in December 2009 .