Troutman Sanders may have some explaining to do, if it doesn’t want to hand over almost $75 million to HSBC Bank USA.

Last week, HSBC filed suit against the Atlanta-based law firm, claiming it acted negligently in advising it on a $100-million securities-backed loan to Hassan Nemazee, who at one time was a wealthy businessman. The bank says a former partner at Troutman Sanders, Robert Chanis, was negligent and breached fiduciary duty to HSBC when he advised the bank to approve Nemazee’s loan. Nemazee, who hails from a wealthy shipping family, pleaded guilty in 2010 to stealing nearly $300 million from HSBC, Citigroup Inc. and Bank of America Corp. He is currently serving a 12-and-a-half year prison sentence for bank and wire fraud.

HSBC’s suit says Chanis failed to fully investigate the securities Nemazee offered to back the loan. Those securities, supposedly worth $89 million, turned out to be fake—leaving HSBC on the hook for $74.9 million.

“We believe the responsibility for this lending decision rested solely with HSBC,” Edward Friedman,  a partner at Friedman Kaplan Seiler & Adelman and lead counsel for Troutman Sanders, told Thomson Reuters. “And that any losses incurred by HSBC were caused by the fraud by Hassan Nemazee and the bank’s own failure to protect its own interest.”

The bank also claims Chanis didn’t bring to its attention to various discrepancies that indicated the securities may have been fake once he learned about them.

“Had Troutman or Chanis done further investigation, they would have discovered that Nemazee did not have a securities account at Pershing LLC and did not own any of the treasury bills that he had pledged as collateral for the HSBC loan,” HSBC said in the suit.

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