The investigation focused on referee Robert Hoyzer and included matches from the 2.Bundesliga, the third-division Regionalliga Nord, and the DFB-Pokal (German Cup) going back to 30 May 2004. Investigators determined that Hoyzer and Marks met regularly with members of a Croatian gambling syndicate run by three brothers, Ante, Filip, and Milan Sapina.
Hoyzer's fellow referees reported him to the DFB after he raised suspicion by making a series of questionable decisions in a German Cup match on 21 August 2004. Upon learning of the investigation, Hoyzer resigned. He later testified that he and Marks had received payment in order to influence the outcome of certain matches. Both Hoyzer and Marks received lifetime bans, with Hoyzer also receiving a 29-month prison sentence and Marks an 18-month prison sentence.
Reportedly, Ante Sapina placed a €240,000 bet on the Karlsruher/Duisburg match and won €870,000. Investigators, however, concluded that while Marks was guilty of attempting to manipulate the match, the attempt did not affect the outcome and the DSB allowed the result to stand.
Duisburg finished in second place that season, earning promotion to the 1.Bundesliga for 2005-06, but returned to the second division the following season.