The 49-year-old was charged with manipulating Duncan into paying a $6 million debt.
While Banks could be forced to repay Duncan for the illegal practices, this is only a fraction of what the former NBA star believes he is owed.
He sued the financial adviser in 2015 for over $20 million for encouraging him to buy into investments that represented a conflict of interest and eventually failed, per Scott Soshnick of Bloomberg.
"Luckily I had a long career and made good money," Duncan said at the time. "This is a big chunk, but it's not going to change my life in any way. It's not going to make any decisions for me."
The two-time MVP and five-time NBA champion retired last season after 19 years in the league.