If the jury believes that Ali, 38, committed premeditated murder, it could sentence him to life in prison without parole or to death.
"There are not a lot of questions that have to be answered in this case," said Barry, who noted that Ali had told police where to find the handgun and that he was the shooter.
If the jury believes that Ali's shooting of the guards was not premeditated, it could find him guilty of second-degree murder, which carries a life sentence without parole but no death penalty.
"We are strongly suggesting that if you intend to execute somebody, you do not have your gun raised at the sky," Bookman asserted.
The evidence will be devastating and could put you in "emotional anguish," he told the jurors. "We just ask that you don't let emotions obscure the facts."
Ali, formally known as Shawn Steele, spent half of the 1990s in federal prison for participating in a string of Philadelphia bank robberies. He is being represented by Bookman and two other public defenders.
The "confession" Ali gave police the day after the slayings will support the argument that his intention was robbery, not murder, Bookman told the jury.
Ali, a father of three from the Northeast, approached guards William Widmaier, 65, and Joseph Alullo, 54, just after 8 a.m. as they serviced the Wachovia Bank drive-through ATM in the parking lot of Roosevelt Mall.
Ali told police that after he ordered the guards to "give up the bag," Alullo reached for his gun, prompting a handgun battle before Ali fled in his black Acura without any money.
Ali fired off eight shots to Alullo's two. Both guards - retired city police officers - died in the parking lot. Barry said that a bullet passed through Widmaier's ribs and hit his heart, and that Alullo was struck in the heart and groin.
Bookman said bank surveillance video showing Ali trying to retreat at one point clears him of first-degree murder.
"You have to fight the presumption of guilt. We ask you to look at the evidence. . . . Make a decision on every single fact," Bookman told the jurors.
Bookman said the defense team is also challenging the fact that Ali has been charged with attempted murder of Loomis driver Joseph Walczak, who was injured by window glass struck by a bullet.
Under cross-examination from Bookman, police crime-scene investigator Leo Rahill said he assumed that the bullet that struck the window had come from Ali's gun even though there was no evidence that it had.
Bookman suggested that Alullo accidentally shot the window and that Ali didn't even know a driver was in the truck.
If Ali is convicted of attempted murder of Walczak - who was 70 at the time and who was scheduled to testify this morning - the prosecution could use that conviction as an aggravating circumstance to help justify a death sentence.