An audit conducted by Germany’s financial regulatory authority, Bafin, revealed that Deutsche Bank - indicted for colluding with Banca Monte dei Paschi di Siena SpA to conceal the Italian lender’s losses - had mismarked the transaction and dozens of others on its own books.

Fact is, regulators found that Deutsche executives had arranged 103 similar deals with a total value of ‎€10.5Bn ($11.8Bn) for 30 clients. The Frankfurt-based lender, Germany’s largest, adjusted the accounting of 37 of those trades in 2013, in addition to Monte Paschi’s, changing them from loans that had been kept off the books to derivatives.

Deutsche Bank’s widespread use of a transaction that’s now the subject of a criminal case highlights the lender’s appetite for complexity at a time when the bank was expanding its fixed-income empire.  While DB has since cut risky assets and eliminated thousands of jobs to bolster capital, mounting legal costs have become a source of increasing concern to investors, driving shares to a record low.

“Very complex deals prevent the market and regulators from properly understanding the state of a bank’s balance sheet, inhibiting proper regulatory monitoring and distorting market discipline,” said Emilios Avgouleas, a law professor at the University of Edinburgh.