That resulted in a mandatory life sentence without parole - the punishment in Pennsylvania state court for first- or second-degree murder. (Some first-degree-murder convictions also can draw death sentences.)
"I was young, ignorant of the law at that time, and I just could not reconcile in my mind how I could be guilty of murder, because I didn't kill anybody - right?" said Werts, now 62.
"So I turned that deal down because I was under the illusion that if I went to trial, I would tell the facts of the case and I would be found guilty of less or I would be found innocent. But I was wrong."
Werts would spend 36 years in maximum-security prison before the state Pardons Board heard his appeal and recommended that his sentence be commuted.
Then-Gov. Ed Rendell signed the order to free him and two other murder convicts on Dec. 30, 2010. Rendell cited the "ancillary roles" the men had played and the fact that some accomplices had more-significant roles but got lighter sentences.
The other two men also spent more than 35 years doing life without parole:
* William Fultz, at age 22, knowingly disposed of the murder weapon used by two of his friends to kill a man in 1974.
* Keith O. Smith, at age 19, was the lookout man during a 1974 robbery that resulted in the murder of a flower-shop owner.
The cases of Werts, Fultz and Smith give insight into why Pennsylvania has the nation's second-largest population of inmates serving life without parole, when crime statistics show that its murder rate is lower than those in 15 other states.
A controversial issue
Given the hefty annual cost of housing inmates - about $32,000 per person - some experts believe that the state should revisit sentencing guidelines to give judges discretion when meting out punishment to those convicted of taking part in murders.
Others say that the concerns of victims' families should take precedence over those of people who have been convicted and sentenced to die behind bars.
"I know that for my families it gives them a little bit more sense of closure when a defendant gets a life sentence and they know that's it," said Tracy Simmons, program director for Families of Murder Victims, a nonprofit organization that works in city courts. "They know they're not going to get a call that they're up for parole."
But state Sen. Daylin Leach, minority chair of the Senate Judiciary Committee, said he is drafting a bill that would make parole possible for some murderers.
The bill, he said, would get rid of the felony-murder rule, which holds that if a murder is committed during the commission or attempted commission of a felony, everyone involved can be convicted of murder.
"I think it is morally problematic to punish people for things that they neither intended to do and did not do," said Leach, a Democrat whose district includes parts of Montgomery and Delaware counties.
"I'm a big fan of courts having discretion, and I am opposed to most mandatory-minimum sentences," Leach added.
The Pennsylvania Prison Society, a nonprofit prisoner-advocacy organization, has long called for changing the law to give some long-serving lifers a second chance at freedom, said executive director Ann Schwartzman.
"You're always going to have some that do need to remain behind bars," she said. "But most people do deserve a second chance, and we at least want to see a process open where people can apply for a commutation or apply for parole and have that opportunity.
"Even in California, Sirhan Sirhan [Sen. Robert F. Kennedy's assassin] and Charlie Manson come up every year for parole."
Second only to Florida
At the end of 2012, Pennsylvania was home to 5,121 inmates serving life without parole. They represented about 10 percent of the state's prison population of about 51,100, according to the state Department of Corrections.
Florida has 7,992 inmates serving life without parole, the most of any state. Louisiana, with 4,637 inmates, is in third place, according to the Sentencing Project, a national nonprofit organization engaged in research and advocacy on criminal-justice issues.
National data indicate that there is no correlation between Pennsylvania's high population of inmates serving life without parole and the number of murders committed in the state.
In fact, 15 states have murder rates higher than Pennsylvania's, and all have fewer inmates serving life without parole, according to the Death Penalty Information Center, a Washington-based national nonprofit research group.
In 2012, Pennsylvania had the 16th-highest murder rate - 5.4 murders per 100,000 people. By comparison, Michigan had the fourth-highest - seven per 100,000 - but had only 3,635 inmates serving life without parole.
But changing Pennsylvania law to give lifers a chance at parole is not on the agenda of state Rep. Ron Marsico, chairman of the House Judiciary Committee.
"These prisons are there for those who commit the most heinous crimes, and releasing them without supervision or parole would be an enormous problem," said Marsico, a Dauphin County Republican. "I'm almost certain the Legislature would not approve that."
He said he would not mind having a study done on the issue with input from sources including Secretary of Corrections John Wetzel and members of the Board of Probation and Parole.
State Sen. Stewart Greenleaf, chairman of the Senate Judiciary Committee, said life-without-parole terms "would be appropriate for certain cases that are so egregious."
In other cases depending on the facts, he said, judges should have sentencing options.
"The more tools we give the judges, the better chance justice will be done," said the Republican, whose district includes parts of Montgomery and Bucks counties.
Most inmates serving life without parole in Pennsylvania are not as fortunate as Werts, Fultz and Smith, who will be on parole for the rest of their lives.
Gov. Corbett has not commuted any life sentences so far. Rendell commuted five, Mark Schweiker commuted one and Tom Ridge commuted none, according to the state Department of Corrections.
"I tell people all the time I'm a walking miracle," said Werts, who stays busy working for the Inside-Out Prison Exchange Program at Temple University and for the Defender Association of Philadelphia.
In May 2013, he won an 18-month fellowship from billionaire philanthropist George Soros' Open Society Foundations to conduct outreach programs aimed at steering ex-offenders away from returning to crime.
"Sometimes I still wake up in the morning and think, 'I cannot believe I'm out here.' "
The North Philly native speaks to organizations throughout the city about prison-reform issues. His work also has taken him to New York; Towson, Md., and Allentown. It's a far cry from his life before he went to prison.
Turned off to school after an elementary-school teacher told him he was too dumb to be an astronomer, Werts dropped out of Simon Gratz High School in the 10th grade.
He amassed an arrest record for street crimes including car theft and drug dealing.
After being convicted of murder and being sent to Graterford, he started to turn things around.
He earned a GED in 1977 and a bachelor's degree in general studies in 1992, and spent 20 years as president of a lifers group whose mission was to change the law so that its members one day could be eligible for parole.
While he was in prison, Werts' parents and three of his eight siblings died.
Some defendants, such as "recreational killers and child-killers," should not get paroled, but others should get consideration, he said.
In his case, he noted, the accomplice who masterminded the 1975 robbery-turned-murder received 10 years' probation for testifying against him and the others.
"That caused me to question: Was this about the prosecutor winning - or was it about justice?"
On Twitter: @MensahDean