Now 78, Dryman was awaiting extradition proceedings Wednesday, a day after his arrest by the Pinal County sheriff's office.
"I think this sends a message to other fugitives that they are never off the radar screen," said Montana Department of Corrections spokesman Bob Anez. "It's imperative that individuals be held accountable for their actions."
Dryman initially received a hanging sentence after a quick trial in 1955. His case became the focus of a battle over the death penalty and frontier justice, and he received a new sentence of life in prison with the help of the Montana Supreme Court.
In 1969, after just 15 years in prison, he was paroled. The Montana Department of Corrections said that today, the soonest a person sentenced to life in prison could gain parole is 30 years.
Dryman disappeared three years later. No Montana offender had been missing longer.
"He just went into thin air in 1972," said Clem Pellett, the victim's grandson. "I don't think that my grandfather's death was well represented; it just got lost in all the ideologic conversation of the time."
Pellett, a surgeon in Bellevue, Wash., pursued the case after first learning details last year while digging through old newspaper clippings in storage. He said the issue was never discussed in the family.
Pellett said he was driven by a sense of curiosity, and does not feel like he needs any revenge since he never knew his grandfather Clarence, and knew little about the murder.
Newspaper clippings from the time say that Clarence Pellett stopped to pick up Frank Dryman in 1951 during a spring blizzard near Shelby, a small town in northern Montana.
Pellett, who ran a cafe, was shot seven times in the back as he tried to run away, according to the accounts.
The private investigator hired by the grandson used scores of documents the family dug up from old parole records, the Montana Historical Society and Internet searches to trace Dryman to the Cactus Rose Wedding Chapel,
Pellett told Montana corrections officials of the discovery. Officials said Dryman acknowledged his identity to officers.
Pinal County Sheriff Paul Babeu said that Dryman had blended into local society and even cultivated friendships with previous county sheriffs.
Prosecutors in Arizona said they did not know if Dryman had an attorney. A call to the wedding chapel Wednesday was not answered.
"They can run from the law, but with perseverance and good investigative work, we almost always find them in the end," Babeu said.
The Montana Department of Corrections said that Dryman will be sent back to the state prison. He will face a parole revocation hearing within the next few months -- and possible resumption of his life in prison sentence.
Pellett said he has learned his family has a long, coincidental history with Dryman. Records show that Pellett's great aunt once testified in support of Dryman when the then 16-year-old was accused of robbing a liquor store.
"She came to his defense so that he was not labeled as a delinquent," Pellett said.
Pellett, who only decided to hire a private investigator on a whim during a dinner party conversation, said he is not driven to see Dryman punished.
"The legal system will handle it," the grandson said. "Whatever they decide is fine with me. I mean he is 78 years old."
But Pellet, 56, said would like to finish writing the family history of the long trial.
"I want to see if he wants to talk to me," Pellett said. "I just want to get information. There are holes in the story he could really add to."