UNION, S.C. (AP) _ Susan Smith whispered, ``I'm so sorry, David,'' after her ex-husband tearfully described how distraught he was after hearing that she had drowned their two sons.

David Smith did not respond to the apology his ex-wife offered Tuesday as she was led from the courtroom during a break in the penalty phase of her trial.

``All my hopes, all my dreams, everything that I had planned for the rest of my life, it ended that day,'' Smith told a jury that must decide whether Ms. Smith will be executed.

``I didn't know what to do. It hurt. Everything I had planned on, my life with the kids, was gone,'' he said as he began to cry.

The prosecution was expected to finish its case today. Unless all 12 jurors vote for execution, Ms. Smith will receive a life sentence. If they decide on death, Ms. Smith would have her choice of the electric chair or lethal injection.

Three jurors wept during Smith's emotional testimony, during which he held photos of his murdered sons in trembling hands. Several times, Ms. Smith leaned over the defense table and cried as her ex-husband spoke about the day he learned his sons were murdered.

Smith, who turns 25 on Thursday, said he believed his then-wife's story that a carjacker had abducted the boys. After a nine-day nationwide search, Ms. Smith confessed Nov. 3 to rolling her car into a lake with 3-year-old Michael and 14-month-old Alex strapped into their car seats.

Defense attorney David Bruck called Smith's testimony ``the most heartbreaking thing I ever heard in a courtroom.''

``But I don't know that the conclusion the jury would draw from that is that Susan should be put in the electric chair,'' Bruck said outside court.

The Smiths divorced in May, but Smith told jurors the marriage was rocky even before their second child was born. Once, when he came home late from work and his wife threatened to return to her mother, he told her she should leave right then.

``Shamefully, I did grab Susan by her arms and just more or less dragged her out of the bed and out to the front porch. Didn't throw her down or anything, just let her down on the porch,'' he said.

After Smith testified, the jury watched two videotaped re-enactments of the crime. Investigators rolled a car like Ms. Smith's into John D. Long lake, where she drowned the boys Oct. 25.

The jurors sat transfixed during the second video, recorded by a camera placed inside the vehicle to show the view the boys had. As the car slowly sank, water poured in under the dashboard, finally overcoming the last air pocket.

Smith's book about the murders was scheduled to go on sale Friday, but by Tuesday many stores already had copies on display.

In ``Beyond All Reason _ My Life With Susan Smith,'' Smith wrote that he first felt sorry for her, but later decided that he could only have a full life again if she were imprisoned for life.

``I don't want to see Susan die. But if it happens, so be it,'' he wrote.

That apparently contradicts his past statements that he wanted his ex-wife to be executed. He was not asked about that Tuesday.

Defense lawyers had been expected to grill Smith about taking a $20,000 advance for the book, as well as abuse allegations. But they decided not to question him.

Bruck said he skipped the cross-examination at the request of Ms. Smith, who told him she wanted to spare her ex-husband any more pain.

Anticipating a cross-examination, Pope had raised the book and abuse issues himself. ``Did you write that book to make money off your children?'' he asked Smith.

Smith replied that he hoped the book would return the public's focus to his dead sons.

``So many people were portraying Susan as the victim,'' he said.