• Whether tainted evidence was used to link Rudolph to the deadly Birmingham clinic blast.
• Apparent problems at a now-closed Bureau of Alcohol, Tobacco, Firearms and Explosives lab that tested evidence in Rockville, Md.
• Whether a model of the bomb reconstructed from fragments found at the Birmingham clinic and in the bodies of the two victims is accurate.

Rudolph was captured after spending five years in hiding as a "mountain man." He is far more relaxed these days, even though he is facing a potential death sentence.

Rudolph's demeanor was in stark contrast to his initial court appearances following his arrest in 2003. Back then, he seemed to stare through walls, people - anything that fell in the way of his cold gaze. But Rudolph was noticeably different during a four-day hearing on scientific evidence this past week, showing glimpses of personality unseen in past court appearances.

"Hey, Michael," Rudolph said with a slight smile to defense lawyer Michael Burt upon entering court one day.

"How's it going?" Burt answered.

"Good," responded Rudolph, who faces the death penalty if convicted of setting off a bomb that killed a police officer outside an Alabama abortion clinic in 1998.

Rudolph has other charges pending as well.

Besides the Birmingham bombing, Rudolph is accused in the fatal bombing at the Atlanta Olympics in 1996 and a pair of bombings in the Atlanta area in 1997.