The former chief executive officer of the failed Enron Corporation, Jeff Skilling, took the stand in a federal courtroom in Houston Monday. He and former Chairman of the Board Ken Lay are on trial for conspiracy and fraud in connection with the December 2001 collapse of the once mighty energy company.

In his first day of testimony, Skilling admitted to being nervous, saying "in some ways, my life is on the line."

He declared his innocence, and vowed to fight the charges against him, until the day of his death, if necessary. Skilling also contended that most of the other Enron officials who pleaded guilty in exchange for their cooperation with prosecutors are also innocent, and made the deals under pressure.

Defense attorneys for both Skilling and Lay have made the same point for the past several weeks, putting blame for the fraudulent schemes at Enron on former Chief Financial Officer Andrew Fastow and others who worked with him.

In their presentation to the court, prosecutors painted a picture of Skilling as a ruthless and cunning corporate official, who approved of those schemes.

But in his comments to the jury Monday, Skilling said he believed Enron was in good financial shape when he left for personal reasons in August of 2001. He said he became concerned by news reports a couple of months later indicating problems in the company, and offered to return. He said his offer was not accepted, however, and the company collapsed in one of the biggest corporate scandals in U.S. history less than two months later.

Skilling's testimony is expected to last all this week.