(Bloomberg) -- Four former bankers at bankrupt Maple Bank GmbH were warned to expect convictions for their roles in so-called Cum-Ex transactions that robbed 388.6 million euros ($441 million) from German taxpayers.

Their trades were set up to cream off refunds for taxes that were never paid, Presiding Judge Werner Groeschel said at a hearing in Frankfurt on Thursday. 

“There’s a high likeliness that all four will be convicted,” Groeschel warned them as he read out a preliminary view of the five judges in the case. “We suggest that you talk to prosecutors to see whether we can now shorten this trial with a view of our preliminary assessment,” he said.   

Germany’s justice system is cracking down on perpetrators of transactions dubbed as a “blatant money grab” by the nation’s top criminal court in July and Groeschel cited that judgment several times at Thursday’s hearing. A court in Bonn has already convicted four bankers in three trials.

Cum-Ex was a trading strategy that syphoned off at least 10 billion euros in government revenue. Named for the Latin term for “With-Without,” Cum-Ex took advantage of German tax laws that seemed to allow multiple investors to claim refunds on a dividend that was paid only once. The nation moved to abolish the practice in 2012.

The Maple bankers dubbed the strategy they ran from 2006 to 2009 the “German Pair.” Initially they organized the trades within the group. Starting in 2008, they added other financial players on the short-seller side, including Barclays Plc, Bank of America Corp.’s Merrill Lynch and Fortis Bank Nederland NV. These banks and Maple prearranged the trades to obtain the illegitimate tax refunds, Groeschel said.

The trial has been pending since May of last year. The next hearing is scheduled for April 4.

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