Others, like Jackie Lee Thompson, came from rural backgrounds. Thompson reacted murderously when the 15-year-old girlfriend he met in foster care lied and said she was pregnant. Thompson, now 57, lives in the state prison at Rockview in north-central Pennsylvania, also serving a life term without chance of parole.
They and about 480 others are all lifers, for crimes committed before they were 18. Most, like Ligon, from Philadelphia, hope the U.S. Supreme Court could give them renewed hope of getting out of prison in something other than a coffin.
Sometime this week, possibly as early as Monday, the nation's high court is expected to rule in two cases that contend it is unconstitutional to sentence someone to life in prison without chance of parole for a crime committed before they turned 18.
The two cases - Miller v. Alabama and Jackson v. Hobbs - are not from Pennsylvania, but legal experts say their impact may be felt more here than in any other state.
Nationwide, about 2,600 inmates are serving life without parole for crimes committed as teenagers. Pennsylvania has more than any other state. Of about 80 nationwide serving life for crimes committed when they were 14 or younger, almost a quarter are in Pennsylvania prisons.
"Most countries don't allow life sentences. The United States allows life without parole for juveniles and Pennsylvania is the leader," said Bradley S. Bridge, a veteran lawyer in the Philadelphia public defenders office who has represented Ligon.
Bridge said he and others in the Defender Association had been working to get the Pennsylvania Supreme Court to review the cases of 350 Philadelphians sentenced to life in prison as teens.
The petition was put on hold by the state Supreme Court pending the U.S. Supreme Court's ruling in the Alabama and Arkansas cases.
For the inmates, scattered among Pennsylvania's prisons, the stakes are high. High enough that Bridge and some other lawyers who represent teen lifers will not allow interviews with reporters; anything they say could be used against them in a future hearing to decide if they should be paroled.
The boom in the number of teen lifers has been building for decades. Julia Glover Hall, a Drexel University sociology professor and coordinator of Drexel's Criminal Justice Program, said she traces the growth in the population of teen lifers to the 1980s.
It was then, Hall said, that the appearance of crack cocaine helped trigger a spike in violent juvenile crime. It also gave birth to a theory by some social scientists that the urban United States would soon face an assault by a generation of "superpredators" - juveniles weaned on abuse, neglect, and violence.
"It never happened," Hall said. At the same time, she continued, neurological research into brain development recognized that teens often commit crimes, even horrific acts of murder, out of immaturity and an inability to appreciate what they are doing.
Unlike adult criminals, researchers concluded, teenage criminals - even those who kill - may yet be rehabilitated and lead productive law-abiding lives outside a prison.
But the scientific research had no impact on Congress and state legislatures, which passed a series of mandatory sentencing laws and others making it easier for prosecutors to petition courts to have juvenile offenders tried as adults.
The research, however, did seem to have an impact on the U.S. Supreme Court.
In 2005, in Roper v. Simmons, the Supreme Court barred the use of the death penalty against juveniles. Five years later, in Graham v. Florida, the court struck down sentences of life without parole for teens convicted in crime other than murder.
In both decisions, the majority opinion was by Justice Anthony M. Kennedy, who wrote that the punishments violated the Eighth Amendment's ban against cruel and unusual punishments.
Kennedy's reasoning relied on what he cited as "the evolving standards of decency that mark the progress of a maturing society."
"No recent data provide reason to reconsider the Court's observations in Roper about the nature of juveniles," Kennedy wrote in the Graham opinion. "Developments in psychology and brain science continue to show fundamental differences between juvenile and adult minds."
Kennedy added that "Juveniles are more capable of change than are adults, and their actions are less likely to be evidence of 'irretrievably depraved character' than are the actions of adults.
Families of the offenders' victims question both the science and the tactics of the teen lifers' advocates, who "continue to tell stories of the offenders who are made out to be merely innocent children sentenced to die," according to a statement issued by the National Organization of Victims of Juvenile Lifers when oral arguments were held in March.
"While we believe natural life sentences for murder should ALWAYS be rare - no matter the age of the offender - it is sadly true that there are some people who are so dangerous that they can never be allowed to walk among us," stated the group, which filed a friend-of-the-court brief in the case.
Even if the Supreme Court invalidates life sentences without parole for teen offenders, juvenile advocates say they don't expect any rush of releases. Pennsylvania has no mechanism for routinely reviewing the question of whether or when lifers may be released.
Drexel's Hall said Pennsylvania could wind up having to amend the law to allow the state Board of Probation and Parole to consider parole for juvenile lifers.
The Supreme Court's ruling could also result in cases of juveniles sentenced to life in prison being remanded for resentencing by the original trial judge.
Under Pennsylvania law, only the governor may commute a life sentence and only after the state Board of Pardons unanimously recommends clemency.
And that rarely happens these days.
Jackie Lee Thompson knows.
In 2005, Thompson's petition for a pardon was before the board. Many felt his chances were good. He behaved in prison, learned several trades - bricklaying, electrician, plumber, mechanic - earned his high school diploma and an associate's degree in business.
Most important, Thompson had his victim's father on his side. Duane Goodwin told the board that he and his wife had forgiven Thompson, calling him "a scared little kid" at the time of Charlotte Goodwin's murder.
A retired facilities manager at the state prison in Camp Hill also told the board that Thompson could live with him if needed and that his son, a plumber, would offer Thompson a job.
The final vote was 4-1 to recommend pardon; the deciding no-vote was cast by Tom Corbett, then the attorney general and now governor. Corbett said Thompson had committed a "cold-blooded murder" and he could not recommend a pardon.
At one time in Pennsylvania, that majority vote by the pardons board would have put Thompson's fate in the hands of the governor.
That ended in 1994 after then-Gov. Robert P. Casey commuted the life sentence of Reginald McFadden after the inmate had served 24 years. McFadden moved to New York and was soon arrested for killing two more people.
Three years later, Pennsylvania voters passed a constitutional amendment requiring a unanimous vote of the Board of Pardons before sending a clemency petition to the governor. The amendment also changed the board's makeup, replacing a lawyer with a crime victim.
From the end of Casey's term in 1995 to the end of Gov. Tom Ridge's term in 2001, the number of lifers recommended for commutation by the Board of Pardons went from 118 to 4 and the number commuted by the governor from 27 to 0.
In the last decade, just one lifer's sentence has been commuted by the governor.
William J. DiMascio, the executive director of the Pennsylvania Prison Society, the nation's oldest prisoner advocacy group - 225 years old and legislatively guaranteed the right to visit any state or county prison in the commonwealth - said he was "appalled" by the Thompson case and the board's ruling.
DiMascio, who has written extensively about juvenile justice reform, said cases such as Thompson's are why he calls the state "Pennsylvania the Merciless."
DiMascio said he visited Thompson last Thursday at the state prison at Rockview, where Thompson is now in his 42d year in prison.
He said Thompson remains hopeful that the Supreme Court overturns laws that let juveniles get sentenced to life without parole.
"It's going to be the happiest day of my life," Thompson said, according to DiMascio. "If they don't rule that way, I'll be disappointed but I'll keep on fighting."
Contact Joseph A. Slobodzian at 215-854-2985, email@example.com, or @joeslobo on Twitter.