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A Barcelona judge rejected Messi's appeal, deciding that Leo had benefited from a scheme set up by his father to defraud Spanish tax authorities of 4.1 million euros ($4.6 million).
Whether or not Messi knew he was breaking tax laws, the judge ruled, doesn't matter.
The question of whether Messi knowingly participated in the fraud, or if it was all his father's idea, will be addressed during his trial.
Messi and his father, Jorge Horacio Messi, are accused of circumventing tax obligations in Spain by using companies in Belize and Uruguay to sell the rights to Lionel Messi's image. Jorge Horacio allegedly set up the scheme when Leo was still a minor.
Father and son have both denied the allegations, and Leo's lawyers have argued that he "has never spent one minute of his life reading, studying, or analyzing" the contracts involved in the scheme.
Prosecutors retorted that Leo had signed the contracts when he turned 18 and was listed as a sole administrator of one of the fraudulent companies in question.
A judge first ruled against Leo and his father in October, stating that "in this type of crime, it is not necessary for someone to have complete knowledge of all the accounting and business operations nor the exact quantity, rather it is sufficient to be aware of the designs to commit fraud and consent to them".
The Messis' appeal of this ruling was finally rejected today. Father and son will appear in court sometime this summer.