HOUSTON -- The trial for former Enron chiefs Kenneth Lay and Jeffrey Skilling resumes on Monday with the defense presenting its side of the case for the first time.

Mike Ramsey, Lay's lead attorney, was absent from court on Monday due to complications from a heart stent implanted on March 24 after experiencing chest pains and a shortness of breath. His condition has not been released.

The government claims both Skilling and Lay repeatedly lied to investors and employees about Enron's strength while accounting tricks covered up massive losses.

Their attorneys said they would show that their clients did nothing wrong and the vilified company was never a bed of corruption.

The lawyers said the cornerstone of the defense is expected to be testimony from Lay and Skilling.

Skilling was expected to be the first of the two former Enron leaders to testify, and he could do so as early as this week.

The defendants say no fraud occurred at Enron other than a few executives who skimmed millions from secret scams. They insist bad publicity and lost market confidence shoved what was once the country's seventh-largest company into bankruptcy protection in December 2001.

Prosecutors rested their case last week after calling 22 witnesses and presenting piles of documents and hours of videotapes and audiotapes.

The defendants appeared undaunted after almost two dozen witnesses bolstered the government's claim that they had committed crimes at the energy trading company.

Outside the courthouse last week, Lay told reporters that he and Skilling are "looking forward to getting on the stand and getting our case out there -- the positive case."

Lay and Skilling have denied any wrongdoing.

Skilling faces 28 counts of fraud, conspiracy, insider trading and lying to auditors for allegedly lying about Enron's financial strength.

Lay faces six counts of fraud and conspiracy for perpetuating the alleged scheme after Skilling resigned in August 2001.

If convicted, each could face decades in prison and millions of dollars in penalties.

The trial is now in its 10th week.