Pinto admits releasing 70 million documents on transactions involving top European soccer clubs. But he argues he is a whistleblower, not a criminal, and is set to call on some extremely high-profile witnesses.
The trial of a Portuguese hacker behind the "Football Leaks" revelations of 2016 began in Lisbon on Friday.
Rui Pinto, 31, is accused of hacking into the computer systems of numerous professional football clubs and intermediaries, to reveal the dealings of clubs, players and agents.
He faces 90 charges, including attempted blackmail, breach of correspondence and data theft.
Pinto's lawyers argue their client has helped authorities confront crime in football, especially murky financial dealings. Pinto insists he was motivated by public duty in exposing serious wrongdoings that had gone unnoticed by authorities.
His lawyers said in a letter to the trial judge that Pinto was "outraged" by illicit money-making in football and looked into what was going on because authorities weren't doing enough.
Pinto says a "substantial part" of the information he revealed was anonymously leaked to him, not hacked.
His lawyers insist he is "a very important European whistleblower" and plan to call 45 witnesses, including Edward Snowden, a former employee of the American intelligence charged with espionage, and the former French financial judge Eva Joly.
Pinto managed to obtain millions of documents and correspondence, which was subsequently published on the "Football Leaks" website, before being sent to media outlets.
German news magazine Der Spiegel was the first to publish material relating to the leaks in 2016. Pinto admits he was behind the documents, but told Der Spiegel he had "acted in good faith."
The trove of information revealed details about the transfer fees and salaries of a number of the game's top players, including Brazil's Neymar, then at Barcelona, Radamel Falcao, who at the time was plying his trade for AS Monaco, and Real Madrid's Gareth Bale.
The documents also alleged that two of the game's heavyweights, Manchester City and Paris Saint-Germain, flouted spending regulations imposed by European football's governing body, UEFA.
Pinto faces 90 charges relating to hacking computers, including at the Portuguese attorney general's office, the Portuguese Football Federation, Sporting Lisbon football club, and Doyen sports management firm.
Sporting Lisbon also accuses him of sabotage, while Doyen alleges extortion.
If found guilty on all counts, Pinto could face decades in prison.