Testimony from former Enron Corp. Chief Executive Officer Jeffrey Skilling at his fraud and conspiracy trial could be pushed back until Monday as questioning of Enron's former top lawyer continued, Skilling's lawyer said Thursday.

Skilling's testimony was expected to begin Thursday afternoon, but his lawyer Dan Petrocelli told reporters "it's looking grim" as to whether his client would take the witness stand before the end of the day.

Skilling, 52, and former Enron Chairman and CEO Ken Lay, 63, stand accused of lying to cover up Enron's decaying financial health as the company that was once the seventh largest in the United States plummeted toward bankruptcy.

Skilling and Lay will both testify in their own defense. Both are expected to argue that Enron was a strong company, and that all its transactions and accounting mechanisms were scrutinized and approved by outside auditors and teams of lawyers.

"I've got nothing to hide. I am innocent of all the charges," Skilling told reporters as he left the courthouse during a lunch break.

Skilling, who faces 28 charges of conspiracy, fraud and insider trading, was a hailed as a business visionary who helped revolutionize energy trading until the company collapsed in a frenzy of scandals in what was the then-largest ever U.S. bankruptcy in December 2001.

Lay, who worked as Enron's CEO for 15 years and again during its final four months before bankruptcy, faces six charges of conspiracy and fraud.

Testimony continued on Thursday morning from Enron's former legal counsel and executive vice president James Derrick, who told the jury he sensed a change in Skilling after the CEO traveled to England in the aftermath of an explosion at the company's plant in Teeside that killed three workers.

"He seemed to me to be, I don't know if depressed is the right word, but changed, just a different demeanor," Derrick said.

Skilling resigned from the company shortly after that trip, having served as CEO for only six months.

Derrick also said under questioning from defense lawyers that Skilling's approval was never required for the deals the company did with partnerships operated by former Chief Financial Officer Andrew Fastow.

Fastow, who will serve a 10-year prison sentence under a plea deal struck with prosecutors, testified earlier in the trial that he set up those partnerships to buy poorly performing Enron assets and help the company inflate its profits.

Fastow said he had a secret agreement with Enron's chief accounting officer that was backed by Skilling that his partnerships — which earned him tens of millions of dollars — would not lose money, but were being used to help bolster Enron's balance sheet.