There's no legal basis for the claim that Troy Davis was wrongly convicted.

His conviction was upheld, over many years, by various appeals courts, and three times by the U.S. Supreme Court, which even delayed the execution at the last minute to be certain of the correctness of the lower courts' decision.

If the "miscarriage of justice" was the existence and imposition of the death penalty, that's another issue entirely.

Troy Davis has nothing to do with the case in Italy.