Local real estate investors are on trial for participating in bid-rigging. Real estate investor and former tennis pro Douglas Ditmer testified on Friday that Community Realty owner Michael Marr was a key participant in a bid-rigging scheme at foreclosure auctions between 2008 and 2011, the East Bay Express reports. Community Realty owns 280 houses and small apartment buildings in Alameda County with a majority in Oakland. Many of these assets were obtained during foreclosure auctions.

Ditmer, who pleaded guilty to conspiracy in rigging bids, said he participated in a scheme where a group of investors would purchase properties at auctions and then sell back the assets to each other and provide kickbacks. Ditmer has identified Gregory Casorso and Javier Sanchez, two of Marr’s business associates, as being part of this activity. Marr, Casorso and Sanchez are all on trial.

The government accused the investors of illegal acts since they would not bid against each other during the public auction, reducing the final sale of properties. The properties would be bid on again in private, illegal auctions. These auctions allegedly cheated banks and taxpayers and people participating in the auctions who were not a part of the scheme.

Ditmer testified the plan would often involve about four properties being auctioned at these illegal auctions daily, often held at bus shelters and other locations far enough away from the initial auction courthouse to provide secrecy.

The FBI investigated the auctions and an undercover officer testified that he went to and participated in 50 auctions with three illegal rounds, according to the San Francisco Business Times.