“It is my view that they improperly influenced trading on the options market, which led to incorrect prices for these financial instruments,” said chief prosecutor Yngve Rydberg at the Swedish Economic Crime Authority (Ekobrottsmyndigheten).

Carnegie reported the three traders to the police after discovering the alleged fraud in the spring of 2007. The investment bank claimed that the illicit activity had caused its trading result to be inflated by 630 million kronor ($89 million) for the period from 2005 to 2007.

But the Swedish Financial Supervisory Authority (Finansinspektionen – FI) questioned the calculation, arguing that it was “not documented in a way that made it possible to check if it was correct.”

An investigation carried out by FI then uncovered major flaws in the running of Carnegie, resulting in a warning, a 50 million kronor fine, and an order for the bank to replace its board and CEO.

FI’s continued probe eventually led to the bank’s nationalization in November 2008 as its licence was revoked.

By the time the police received the bank’s report on the suspects’ alleged wrongdoing, one of them had already left Carnegie of his own accord. The two remaining suspects were sacked.

Both men later sued for unfair dismissal before Carnegie responded with its own large claim for financial damages. The parties eventually settled their labour dispute out of court last spring, but Carnegie remained adamant that a crime had been committed.

Yngve Rydberg explained the lengthy nature of the investigation by the fact that it had involved thousands of share option deals.

“The original reports concerned an incredible amount of material,” he told news agency TT.

The indictment however focuses on tens rather than thousands of deals.

All three suspects deny the charges against them.