In one of the country's biggest corporate trials, Ackermann told a regional court in the western city of Düsseldorf that his approval of huge bonuses following the takeover of German telecommunications giant Mannesmann in 2000 were ethical and legal.

If he had believed there was "even the smallest bit of evidence" for the giant payouts being illegal, the defiant Ackermann said, "I would never made the decision I did, especially considering that I had no vested interest."

Ackermann, 58, stands accused along with five other top-ranking executives of breach of fiduciary duty for signing off on the bonuses.

The case put executive pay in Germany in the spotlight and raised ethical questions about the successful transformation of Mannesmann from an industrial conglomerate into a huge mobile telecommunications group.

Would quit if found guilty

Although the six defendants were initially acquitted in July 2004, the federal Constitutional Court ordered a retrial at the end of last year. Ackermann, who is Swiss, has indicated he would quit his position as head of Deutsche Bank if found guilty this time.

Ackermann, along with former Mannesmann chairman Klaus Esser, Mannesmann's former supervisory board chief Joachim Funk, the former head of the powerful IG Metall labor union, Klaus Zwickel, and two others, Jürgen Ladberg and Dietmar Drost, are accused of breaking the law by approving a total 111.5 million marks (57 million euros, $72 million) in payouts to former Mannesmann executives.

Original trial ruled payouts were not criminal

Esser himself pocketed 16.4 million euros. In the original trial, the court ruled that while the size of the payouts went against Mannesmann's interests and were therefore not admissible under German stock law, they did not constitute criminal action, as claimed by the prosecution.

At the time of the Mannesmann payouts, Ackermann was a member of the group's supervisory board.

He has become a highly unpopular figure in Germany, and was lambasted for slashing thousands of jobs while Deutsche Bank posted record profits.