A teacher accused of goading three teenage students - including her lover - into killing her husband told them not to hurt her dog or get blood on her sofa, one of the killers testified.

Patrick Randall, 17, also told how he held the victim by the hair while another of the teenagers pulled a gun, said "Forgive me, God," and shot the man in the head on May 1.Randall's testimony Tuesday followed opening statements in which defense attorney Mark Sisti charged that the three youths - who plea-bargained to avoid possible sentences of life in prison without parole - conspired to kill Gregory Smart and now are conspiring against his widow to save themselves.

Pamela Smart, 23, a former media coordinator at Winnacunnet High School, is charged with murder conspiracy and accomplice to first-degree murder in the slaying of her 24-year-old husband. She faces life in prison without parole.

Randall, William Flynn, 16, and Vance Lattime, 18, all of Seabrook, admitted killing or helping kill Smart and pleaded guilty to second-degree murder and accomplice to second-degree murder. Randall said he faces 28 years to life.

Randall testified that Mrs. Smart saw murder as the more profitable way out of her marriage. "She did not want a divorce because if she got a divorce, she wouldn't get any money," he said.

Randall outlined how he and Flynn entered the Smarts' Derry condominium while Lattime and another teen waited in a parking lot. Randall said Flynn grabbed Smart when he walked in. Randall then seized the victim's hair and forced him to his knees while he pleaded for mercy.

"I was supposed to stab him," Randall said. "I couldn't do it."

So Flynn motioned toward the gun he stashed in his waistband, and Randall nodded, the witness said.

"He took the gun out. He held the gun a couple of inches from (Smart's) head, said, `Forgive me, God,' and shot him," Randall said.