Cesare Pagano and Rito Calzone ordered and executed the killing of 43-year-old Carmine Amoruso, who was shot dead in a bingo hall in Mugnano near Naples in 2006, Football Direct News reported.
Calzone was sentenced to 14 years in prison by a court in Naples in 2010 following a bloody turf war between rival gangs that spiralled out of control.
Calzone, though, claims he was in Barcelona to watch Chelsea take on the Catalans in the Champions League with his lawyers now producing pictures of him posing alongside Mourinho and several Chelsea players, including Lampard and Hernan Crespo in Barcelona.
The pictures were taken at the luxury Arts Hotel, where the London team was staying ahead of the match against Barcelona.
Calzone along with associates of his gang reportedly paid for three suites at the hotel.
The pictures, hotel receipts and plane tickets all form part of the appeal case.