HOUSTON – When former Enron Corporation Chief Executive Jeffrey Skilling gives his much-anticipated testimony in his fraud and conspiracy trial, the stakes may be just as high for the government as they are for the onetime corporate star.

For Mr. Skilling, testimony expected to begin today is his chance to show jurors he is not a devious liar who spearheaded a massive fraud.

For prosecutors, it’s a chance to drive home their contention that he is.

“His testimony may be his only opportunity to save himself, but at the same time, he runs the risk of sealing his fate and almost guaranteeing his conviction if jurors find his testimony incredible,” a former federal prosecutor, Robert Mintz, said.

Mr. Mintz said Mr. Skilling can expect cross-examination far more rigorous than softball questions he used to field from Wall Street analysts who adored Enron before the company collapsed in scandal. “His ability to handle these questions without appearing arrogant or defensive may be the key to his testimony,” he said.

Mr. Skilling’s co-defendant, Enron founder Kenneth Lay, aims to testify later this month.

In lengthy testimony with Securities and Exchange Commission and two contentious appearances at congressional hearings in February 2002, Mr. Skilling said he knew of no accounting tricks to hide debt or inflate profits. He also insisted he believed Enron was financially strong when he abruptly resigned in mid-August 2001, citing personal reasons.

Under initial questioning by his lead lawyer, Daniel Petrocelli, Mr. Skilling won’t deviate from what he said before – or he’ll invite prosecutors to pounce on inconsistencies.

He’ll counter allegations from prosecution witnesses that he approved use of accounting tricks to manufacture earnings and misled investors by touting weak business ventures as strong.

He’ll tell jurors that he loved Enron, he offered to return to help save the company when a storm of scrutiny erupted after he quit, and he relied on accountants and lawyers who consistently said all the company’s inner workings were proper, as Mr. Petrocelli noted in opening statements more than two months ago.

Whether Mr. Skilling’s reputation for bristling when annoyed emerges during his testimony remains to be seen. Mr. Petrocelli has said his legal team has not tried to water down Mr. Skilling’s personality because “witnesses need to be on the witness stand who they are in life.”

Prosecutors likely won’t try to bait Messrs. Skilling or Lay and shoot for so-called “Perry Mason” moments, said Sam Buell, a former federal prosecutor with the Justice Department’s Enron Task Force.

“They’re going to be confronted for the first time with lots of detailed questions that they didn’t face before because the questioners didn’t know all the facts yet,” Mr. Buell said. “The question will be, how do they react to a more detailed level of inquiry that they haven’t faced before?

“It’s going to be the task of the crossexaminer of cumulatively undermining credibility with lots of small points, not coming up with some big bombshell that’s going to leave one of these guys exposed on the witness stand in some dramatic way,” Mr. Buell said. “It’s just not going to happen that way.”