Pennsylvania state inmate BB8134 was expecting someone else.

From time to time he had a woman visitor at Graterford Prison, and when he ambled into the guests' lounge that morning back in September 2007 and spotted me with my notepad, his look said, who the hell are you?

He sat with me anyway, and talked about what it felt like to be charged with murder, 41 years after shooting a cop.

William J. Barnes didn't look to me like a danger to society, but that wasn't the reason he was being tried. He looked more like a 71-year-old supermarket stock boy (the job he held at the time he was picked up), a little stooped, a little bewildered.

He had a career criminal's understanding of the law: You shove someone on the sidewalk and they happen to fall into the path of an oncoming car, you're responsible for their death. What Barnes had done was worse than that.

While burglarizing a beauty shop in 1966, Barnes shot Walter T. Barclay, a 23-year-old rookie police officer.

Barclay never walked again. He was a victim, a prisoner now of his own uncooperative body. He died in 2007 from an infection the state contended was a direct result of the bullet Barnes fired.

When prosecutors decided that the two decades Barnes had served were not enough, I never ventured an opinion on whether they were going too far. I couldn't.

I was a state witness.

By getting Barnes to talk about the shooting, I wound up providing a potentially key link in the evidence.

Barnes told the story that day at Graterford as if he'd been rehearsing it for years.

"Let me tell you how it happened," he began. "It was Nov. 27, 1966. I was drunk. I was carrying a weapon. . . ."

He had wandered in back of some storefronts around Fifth Street and 66th Avenue in East Oak Lane. "I just started kicking in these doors. I didn't even know it was a beauty salon, that's how loaded I was."

A woman upstairs hollered, he said, and out of nowhere the rookie cop appeared, whacking Barnes in the face with a flashlight.

"I sobered up immediately," he said. "I got the hell up those steps."

Barnes had a gun. He told me he had intended to use it to disarm the cop, maybe bluff his way out of the jam. After years of being in and out of jail, he didn't want to go back.

He grabbed Barclay's coat and pulled the officer close. Barclay spun free and his partner came into Barnes' view. Barnes fired twice.

"Now, I'm totally committed," he told me. "I just shot at random, twice, in Barclay's direction. One hit his leg, the other his upper shoulder."

Barnes had never told any of this story to the court. He'd pleaded not guilty and didn't testify, as was his right. So the prosecutor wanted the option of using my account to establish the chain of events that he said caused Barclay's death.

I had to answer his questions in front of a grand jury. I relayed what I had put in the paper after my jailhouse interview. The prosecutor didn't force my hand and ask me to say more.

Ultimately, he didn't need me. Barnes did stipulate that he had shot Barclay - but maintained that he was not responsible for the officer's death. Too many other factors, he argued, could have caused the infection.

Monday, a jury of his peers agreed with Barnes.

Until today, I've been unable to say how bad I felt about trying the man twice for the same act, after he'd served his time.

I've always thought that decision was wrong. Would he have been charged again had his victim not been a police officer? I don't think so. I would have expected Lynne Abraham's successor, Seth Williams, to put the brakes on the prosecution. I was optimistic.

That day in prison, Barnes said something that made me wince. He thought it was unfair to be charged again.

"For the first time, I feel like a victim," he said.

Incredible words from a career criminal.

The state never should have given him the satisfaction of saying them.