The appeal by Confederation of African Football (CAF) president Ahmad against his five-year ban from football by FIFA has begun at the Court of Arbitration for Sport (CAS) in Switzerland.
Ahmad is hoping to overturn the ban in a bid to be registered for next week's CAF presidential elections.
The 61-year-old from Madagacar, who dethroned long-standing CAF ruler Issa Hayatou in 2017, was banned in November after football's world governing body adjudged him to have breached several of its ethics codes.
Ahmad was dramatically restored to the CAF presidency three months into his ban after CAS effectively said the possibility of his winning his appeal should not prevent him from being able to campaign for the elections, issuing a preliminary ruling.
Despite being legally returned to his position as both CAF president and FIFA vice-president, Ahmad has not yet been classified an eligible candidate for the elections as the Zurich-based world body awaits a definitive ruling.
CAS - whose hearing is expected to last one day, possibly two - has said it will "render a final award shortly after the hearing, i.e. before 12 March 2021".
A reduced sentence, which may still rule Ahmad out of the elections, is considered a likely outcome in the trial, for which FIFA recently bolstered its legal team.
Four candidates have been approved for the elections: Jacques Anouma (Ivory Coast), Patrice Motsepe (South Africa), Augustin Senghor (Senegal) and Ahmed Yahya (Mauritania).
FIFA found Ahmad - who was once proclaiming the backing of 46 federations - to have broken ethics rules relating to duty of loyalty, the offering and accepting gifts, abuse of position and misappropriation of funds.
These were primarily related to a decision to approve deals totalling $4.4m with a French company run by a close friend of Ahmad's then attachÃ© and the financing of a religious pilgrimage to Saudi Arabia for Africa's Muslim FA presidents.
CAF's 2021 presidential elections are set to take place in the Moroccan capital Rabat on Friday 12 March.