Instead, the prosecution has kept the 64-year-old Mr. Lay on the defensive by largely avoiding Enron's financial labyrinth and challenging him on easier-to-understand matters.

For example, the defense has blamed short-selling "vultures" -- seeking to profit from a decline in Enron shares -- for driving down the stock in 2001 and helping spark a market panic that killed the company. That line blew up in their face on Thursday when prosecutor John Hueston³ showed embarrassing evidence that Mr. Lay's own son, Mark, had sold the stock short in March 2001.

Not all has gone badly for Mr. Lay. He and Mr. Secrest have raised doubts about allegations made by some government witnesses. For instance, after a former Enron executive testified for the government that she and Mr. Lay had an incriminating conversation while riding in a car in New York, Mr. Secrest rebutted the claim by showing parts of Mr. Lay's Enron travel schedule.

It's impossible to know what impression Mr. Lay is making on the 12 women and men who will decide his fate. But his rockier-than-expected performance could change the trial's dynamics.

Mr. Lay had the misfortune more than midway through the trial of losing his lead lawyer, 66-year-old Michael Ramsey, to heart and related health problems. Mr. Ramsey, known for his aggressive courtroom theatrics, has a reputation as one of the best criminal defense attorneys in Texas. Though Mr. Secrest, 54, had been part of the defense team, he and Mr. Lay had little time to work together on the testimony and didn't seem to develop a rapport or rhythm during three days of questioning last week.

Despite going through an estimated $20 million, the Lay defense team appeared unprepared for some of the prosecution's zingers. Mr. Hueston tore into Mr. Lay for making monthly public filings in 2001 that failed to show he was selling about 1.7 million Enron shares, two-thirds of his holdings. Mr. Lay repeatedly responded that because the stock was sold back to Enron, company attorneys assured him he wasn't required to report the transactions until year-end. Mr. Lay so often pointed to reliance on advisers that Mr. Hueston mockingly asked if he felt he'd been "brainwashed" by underlings, bringing a sharp denial.

Complicating the picture, say people familiar with the matter, there are indications Mr. Lay has increasingly taken control of his defense strategy. This could help explain why he made calls as recently as a few weeks ago to potential witnesses. The calls left him open to prosecution allegations of attempted witness tampering, although he isn't charged with that and he heatedly denied it.

Mr. Lay approached one government witness, former Enron Treasurer Ben Glisan Jr.⁴, to offer kind words during a bathroom break. Yet, outside the courtroom talking with news media, Mr. Lay described Mr. Glisan, who is in prison for an Enron-related crime, as a liar. Mr. Ramsey compared him to a "performing monkey."

Some attorneys not involved in the case said a criminal defendant shouldn't be contacting witnesses. "Any lawyer would discourage it with a heavy foot. To me, Lay did it on his own," said Mark Zauderer, a business-trial lawyer. A Lay spokeswoman said members of his legal team were too busy with the trial to respond to press questions. She later sent an email blaming Mr. Hueston for "raising unrelated matters that have nothing to do with the case. We feel the jury will see through this maneuver."

To some observers before the trial began on Jan. 30, Mr. Skilling -- intense, sometimes abrasive -- appeared more likely than Mr. Lay to melt down on the stand and possibly hurt both himself and Mr. Lay. While Mr. Skilling hardly came through eight days on the stand unscathed, some trial observers thought he did better than Mr. Lay has so far. Now some wonder if Mr. Lay's performance might generate headaches for Mr. Skilling. For instance, Mr. Lay said Mr. Skilling was far more detail-oriented -- not a welcome description in a case about financial manipulation.

With another day or two left on the stand this week -- the jury may get the case around mid-May -- Mr. Lay has little time to steady a defense effort four years in the making. He retained Mr. Ramsey in late 2001, long before his indictment. Mr. Lay stayed mum as he was hauled in front of congressional committees and pilloried for invoking his Fifth Amendment privilege against self-incrimination. Mr. Skilling talked extensively with investigators, and some answers he gave to the Securities and Exchange Commission have been used against him at the trial.

Mr. Ramsey is a near-legend in Houston legal circles, with victories including acquittal for a client who killed a man and threw body parts into Galveston Bay. (Mr. Ramsey and colleagues convinced jurors a gun went off accidentally during a struggle.) Under Mr. Ramsey's leadership, Mr. Lay spoke publicly only after his July 2004 indictment, then pushed the notion he was the victim of a government vendetta. The Lay camp blasted the Justice Department's Enron Task Force and its former director, Andrew Weissmann.

Mr. Lay showed his distaste early on for Mr. Hueston, the 41-year-old federal prosecutor. In his opening statement, Mr. Hueston accused Mr. Lay of having borrowed $1 million from Enron days before its bankruptcy filing and having never repaid it. The action showed "Lay wasn't prepared to sacrifice himself," he said.

Asked about it by his own attorney last week, Mr. Lay testified that he had worked out a repayment deal in the bankruptcy proceeding. "And it was not finalized because John Hueston blocked that deal," Mr. Lay said angrily as he pointed at the prosecution table. Mr. Hueston objected, calling the statement "just outrageous" and adding, "I wish I had such power." His objection was sustained and Judge Sim Lake told the jury to disregard Mr. Lay's comment.

When Mr. Ramsey's health problem arose, Mr. Lay could have asked for a mistrial. "It's no easy task for another lawyer in a complicated trial to shift gears and take on a role for which he has not been preparing," notes Joseph Beeler, a past president of the American Board of Criminal Lawyers. But when Judge Lake asked if the defense wished to continue without Mr. Ramsey, a defense lawyer said, "We're good as we're going, your honor."

Mr. Secrest is a former county prosecutor and the team's appellate specialist, who prepares briefs. He too has worked in high-profile cases and is highly regarded. But unlike the roguish charm and jury skills of Mr. Ramsey, Mr. Secrest has a somber demeanor and bland style better suited to judges than juries.

The overall strategy was determined before Mr. Ramsey had to bow out. He confers with the legal team as he recovers from two surgical procedures to correct heart and circulatory problems, say people familiar with the defense team.

Some thought Mr. Lay's problems last week lay more with the witness than his questioner. When not on the stand, Mr. Lay often leans back and looks relaxed, frequently smiling or even laughing in lighter moments. But in four days on the stand last week, he rarely looked at the jury and struggled to smile, violating a cardinal rule of witnesses hoping to gain a jury's trust.

Asked by his lawyer about the impact the bankruptcy proceeding had on him, Mr. Lay waxed on about how "devastating" it had been to him after decades of business success, noting that in his career he had contributed to "changing energy policy in this country and a few other countries." Only at the end of a long answer did he mention that "the most painful part" was seeing thousands of Enron workers and retirees lose their jobs and savings. He gave the whole answer in a relatively flat and emotionless tone.

Though he testified at length and with justified pride about his rise from humble roots in rural Missouri, he occasionally couldn't resist a not-so-humble boast. He noted he'd been invited to join an investment bank advisory board -- then added that it was "a very small but very prestigious advisory board."

Mr. Lay "has to be faulted to a much greater extent than Secrest," contended Christopher Bebel, a Houston securities attorney. "Lay has been his own worst enemy."

The defense has complained publicly that few former Enron executives would testify for Mr. Lay. People close to him say he is offended by the unwillingness of some civic leaders and politicians to appear in the courtroom alongside his family. Mr. Lay has a long history of supporting politicians and civic causes in Texas.

Some defense initiatives have seemed to backfire. Realizing jurors might resent Mr. Lay for all the money he made, Mr. Secrest tackled this head on. He flashed some of Mr. Lay's income-tax forms, showing he made as much as $100 million annually, onto a large courtroom screen. He then walked over to a small easel and began explaining to jurors how stock options worked. But many kept their eyes on the screen with Mr. Lay's big income numbers.

The defense failed to deal with other potentially damaging matters. Mr. Hueston pressed Mr. Lay on a $120,000 investment he'd made in a small Internet company called PhotoFete.com Inc. Mr. Lay said he couldn't recall much about it but grudgingly conceded he probably should have told Enron about a potential conflict of interest, since the small company did business with Enron.

"You guys are pretty thorough," said Mr. Lay, evoking a "thank you" from Mr. Hueston. Mr. Secrest was reduced to unsuccessfully objecting to the questions.

The defense's failure to address that issue seemed odd, as it had also caused Mr. Skilling trouble in his witness stint. The government had shown that Mr. Skilling not only invested in PhotoFete without telling Enron, but also dated the woman who ran the firm and apparently backdated a $10,000 check to her, possibly for tax reasons. Though Mr. Skilling heatedly denied wrongdoing, many observers believed it was one of the more damaging episodes of his testimony.

The cross-examination of Mr. Lay continues today. Then Mr. Secrest will get a second, though more confined, round of questioning with Mr. Lay, who has had a weekend to see if he can turn things around. Mr. Bebel, the Houston securities lawyer, predicted Mr. Lay would "redouble his efforts to manifest a more reasonable and personable businessman."

Write to John R. Emshwiller at john.emshwiller@wsj.com²⁹ and Gary McWilliams at gary.mcwilliams@wsj.com³⁰