Terry Nichols (search) deserves execution by lethal injection for helping with the deadly bombing of the federal building in Oklahoma City, a prosecutor told jurors Tuesday as the penalty phase of Nichols' murder trial got under way.

Nichols, who was convicted in state court Wednesday of 161 counts of first-degree murder, "constitutes a continuing threat to society," prosecutor Sandra Elliott said.

Defense attorney Creekmore Wallace urged the jury to listen to all of the evidence and consider all sentencing options before deciding whether Nichols should be sentenced to death or to life in prison.

He said defense attorneys will give jurors a glimpse of Nichols' life before and after the bombing, including his relationships with his two former wives, his three children and his large extended family in Michigan.

"Terry worked hard at these relationships," Wallace said.

Before the sentencing phase began, Judge Steven Taylor ruled that rescuers could testify about the experiences of victims of the bombing. Defense attorneys wanted to block testimony from about 20 rescuers who are among dozens of people expected to testify.

Nichols' jury found him guilty of 161 counts of first-degree murder on Wednesday, just five hours after they began deliberating.

Jurors also found him guilty of first-degree arson and conspiracy to commit arson in the April 19, 1995, bombing of the bombing of the Alfred P. Murrah Federal Building (search), which killed 168 people and injured hundreds more.

Nichols, 49, was acquitted of federal murder charges in 1997 but convicted of conspiracy and involuntary manslaughter charges in the deaths of eight federal law enforcement officers in the bombing. He was sentenced to life in prison.

Oklahoma prosecutors charged Nichols in 1999 with the deaths of the 160 other victims and one victim's fetus.

Taylor barred prosecutors from seeking the death penalty on the count involving the fetus after ruling prosecutors did not give his attorneys adequate notice of their plan to seek the death penalty on that count.

Nichols' jury sentenced him to life in prison without parole on that count.

The penalty phase of Nichols' trial is expected to last about three weeks. Prosecutors will question dozens of bombing survivors and members of victims' families about the impact the blast had on their lives.

Nichols' relatives, including mother, Joyce Wilt, and sister, Suzanne McDonnell, are expected to plead for his life. Nichols, who did not testify in his own defense, could still testify during the penalty phase.

Nichols was found guilty after prosecutors presented evidence that he bought the explosive ammonium nitrate fertilizer used in the homemade bomb that destroyed the Alfred P. Murrah Federal Building and stole detonation cord, blasting caps and other explosives.

The defense contended others helped executed bomber Timothy McVeigh (search) carry out the bombing and Nichols was the fall guy for a wider conspiracy.