Ruth married and settled in Irving, Texas. Her husband, Michael Paine, found employment as a research engineer with the Bell Helicopter Company, whereas Ruth was employed as a part-time teacher of the Russian language at St. Marks School in Dallas.
In 1963 Michael Paine left the family home. According to the author Jim Bishop (The Day Kennedy Was Shot), it was a "friendly estrangement". Ruth continued to live in Irving and at a party in February, 1963 she was introduced to Marina Oswald and Lee Harvey Oswald by George De Mohrenschildt. On 24th April, 1963, Marina and her daughter went to live with Ruth Paine. Lee Harvey Oswald rented a room in Dallas but stored some of his possessions in Ruth Paines garage. Ruth also helped Oswald to get a job at the Texas School Book Depository.
On 31st October, 1963, an FBI agent, James Hosty visited Paine's home to discover where Oswald was living. He spoke to both Paine and Marina Oswald about Lee Harvey Oswald. When Oswald heard about the visit he went to the FBI office in Dallas. When told that Hosty was at lunch Oswald left him a message in an envelope.
The contents of the envelope has remained a mystery. A receptionist working at the Dallas office claimed it included a threat to "blow up the FBI and the Dallas Police Department if you don't stop bothering my wife." Hosty later claimed it said: "If you have anything you want to learn about me, come talk to me directly. If you don't cease bothering my wife, I will take appropriate action and report this to the proper authorities."
According to fellow worker, Dave Noel, Michael Paine discussed the "character of assassins" a few hours before President John F. Kennedy was killed. He also returned to his home in Irving at 3.00 p.m. to find Dallas police officers searching the premises. He told the police: "As soon as I found out about it, I hurried over to see if I could help."
Anthony Summers reported in his book, The Kennedy Conspiracy that Michael Paine was overheard talking to his wife on the phone. He said that he was sure that Lee Harvey Oswald had killed John F. Kennedy. He added: "We both know who is responsible."
Buddy Walthers took part in the search of the home of Ruth Paine. Walthers told Eric Tagg that they "found six or seven metal filing cabinets full of letters, maps, records and index cards with names of pro-Castro sympathizers." James DiEugenio has argued that this "cinches the case that the Paines were domestic surveillance agents in the Cold War against communism."
Ruth Paine was a key witnesses for the Warren Commission and provided detailed information on the activities of Marina Oswald and Lee Harvey Oswaldbefore the assassination. Jim Garrison later suggested that Ruth Paine might have been involved in setting Oswald up as the "patsy". Garrison points out that Paine's father " had been employed by the Agency for International Development, regarded by many as a source of cover for the C.I.A. Her brother-in-law was employed by the same agency in the Washington, D.C. area." He also claims that he had tried to "examine the income tax returns of Ruth and Michael Paine, but I was told that they had been classified as secret.... What was so special about this particular family that made the federal government so protective of it?"
In 2002 Thomas Mallon wrote a book about Ruth Paine's involvement in the case, Mrs. Paine's Garage and the Murder of John F. Kennedy. Unlike Jim Garrison Mallon took the view that Paine was completely innocent of any involvement in the Kennedy assassination conspiracy.
Ruth Paine has worked for a Nicaraguan relief group in St. Petersburg, Florida. She is also a peace activist. In 1982 she claimed: "This year, for the first time, I am withholding that portion of my income tax (40 percent), which I estimate goes toward military uses and war preparations" In 2004 she was interviewed by the St. Petersburg Times: "I believe in taxation. I believe in government.. But I also believe in our right to religious freedom. And I believe in the fact that we value dissent as a patriotic thing."