Former FIFA secretary general Jerome Valcke is testifying at the Court of Arbitration for Sport to challenge a 10-year ban from soccer for unethical conduct.
The CAS appeal hearing on Wednesday is expected to last eight hours. A verdict is likely within weeks.
Valcke, who was a FIFA marketing executive before becoming then-President Sepp Blatter's right-hand man in 2007, declined to comment to media outside the court.
Valcke was fired by FIFA in January 2016 after being implicated in irregular World Cup ticket and broadcast rights sales, plus expense abuses including personal use of private flights.
The FIFA ethics committee banned him for 12 years, with an additional charge of destroying evidence. FIFA's appeal panel cut the ban by two years because it judged the broadcasting deal charge was not proven.
Valcke, a French former TV presenter, denies wrongdoing and is also under criminal investigation by Switzerland's attorney general. Proceedings were opened against Valcke in March 2016 ''on suspicion of various acts of criminal mismanagement.''
A separate FIFA ethics case was opened in September 2016 to investigate Valcke, Blatter and former FIFA finance director Markus Kattner over contracted bonuses. Some World Cup bonuses over $10 million were due to be paid, and had been signed off by other FIFA officials.
Valcke's main role was overseeing the troubled preparations for the ultimately successful 2010 and 2014 World Cups hosted by South Africa and Brazil, respectively.
The FIFA ethics investigation was provoked by allegations in September 2015 that Valcke sought to profit from a black market ticket deal for the World Cup in Brazil. The deal, with a contracted FIFA ticketing partner, later fell through and no money was paid.
The South African connection implicated Valcke in the U.S. Department of Justice indictment which has rocked FIFA, and eventually removed Blatter, since it was published in May 2015.
In 2008, Valcke's office transferred $10 million on behalf of South African World Cup officials to senior FIFA officials in North and Central America. American federal prosecutors allege they were payments in a bribery conspiracy for World Cup hosting votes.
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