"This whole thing doesn't even make sense, let's be honest," Assistant District Attorney John Whelan told the jury in his summation. "This killing never, never should have happened."
An enraged Nixon went to the A.R.M. lot that sweltering afternoon with his girlfriend after receiving $300 in traffic citations on a junked car he had turned over to the towing company six months earlier, according to testimony.
The girlfriend, Theresa Duncan, testified that she and McGowan stood and watched Nixon for nearly 20 minutes as he vented his anger about the tickets on his old 1976 Grand Prix, thoroughly smashing it with a hammer.
Duncan told the court that McGowan was polite, handed Nixon the hammer, and even exchanged small talk about the weather.
Duncan said McGowan at one point walked off. She said she next heard two shots and saw McGowan standing with a rifle in Nixon's chest as Nixon knelt beside the right front tire of the Grand Prix.
She said McGowan fired once, stood over Nixon's body and "continued to shoot him. . . . Every time he shot him his head would jump."
"That's first-degree murder," Whelan argued. "It was 90 degrees that day, but I submit to you the temperature in that man's heart was below zero."
McGowan testified he got the .22-caliber rifle from his car trunk, fired two warning shots as Nixon rummaged through the towing company's supply truck and ordered Nixon off the lot.
Nixon then came at him and, McGowan said, "I was terrified."
McGowan said he "pumped six shots rapidly into his body." He acknowledged firing three of the shots into Nixon's head from four feet away as Nixon lay on the ground.
Raymond Williams, assistant public defender, argued that McGowan was justified in the shooting and said McGowan produced the rifle to scare off Nixon, not to shoot him.
McGowan did not take the stand in his first trial in January when Williams argued that his client was both insane and acting in self-defense when he shot Nixon.
The January jury deadlocked on the murder charges and found McGowan guilty, but mentally ill, of possessing the rifle.
Whelan had conceded that McGowan was mentally ill, but argued he was not insane during the shooting.