The relic of the Polish pope who died in 2005 and was canonised in 2014 was stolen in September from the cathedral in Spoleto, in the centre of Italy.
Local police told AFP they filed charges for theft against a 59-year-old man from Tuscany, known to police for having stolen other sacred relics in the past. The man was not arrested.
Video surveillance taken inside the church and in city streets helped authorities identify the man.
The relic remains missing, however, after a search of the man's home revealed no traces of it, police said.
The golden cross with a vial of the former pope's blood was given to the Spoleto-Norcia archdiocese in 2016 by the Polish cardinal Stanislaw Dziwisz, who served for years as John Paul II's personal secretary.
The relic was displayed in a niche of the cathedral, protected by an iron gate, whose alarm did not sound after the theft in broad daylight.
The alleged thief then headed to the train station where he took two trains to return home.