In 1954, they moved to Denver, Colorado, where his father got a job as a sandblaster at Buckley Air Force Base.

Lyle argued he was being attacked with a lead pipe and was not the one who pulled the trigger, but he was convicted of second-degree murder[4] and sentenced to 15-to-25 years in the Colorado State Penitentiary.

[4] In solitary confinement for 90 days afterward, he began doing push-ups, sit-ups, squats, and other exercises, and he trained regularly from then on.

Lyle credited Lt. Cliff Mattax, the athletic director at the prison, for developing his interest in boxing.

[citation needed] According to Colorado State's Warden Wayne K. Patterson, Lyle was a "natural born athlete.

"[5] During the remainder of his sentence, he had around twenty-five unaccounted amateur fights, losing only once, and winning six heavyweight titles for inmates.

Bill Daniels, a cable television executive, president of American Basketball Association and owner of the Denver Rocks boxing team and the Utah Stars basketball team, offered Lyle an official job as a welder with a firm he owned, and on Sunday, November 9, 1969, Lyle was released from prison on parole.

He made the team, and in the succeeding fifteen months, before turning pro, he won a number of tournaments.

Lyle's first amateur victory was a third-round knockout over Fred Houpe (who would later be Leon Spinks's final opponent).

After capturing the NAA title, Lyle became a member of the United States National Boxing Team,[13] as he was still on parole he was given permission to leave the U.S.,[14] and dispatched on a boxing journey across Europe, visiting Italy, Yugoslavia, and Romania and meeting top local heavyweights in the process.

[15] He lost by decision to Romanian Ion Alexe, but pounded Soviet Armenian heavyweight Kamo Saroyan (89–9[16]) against the ropes (referee interrupted and saved Saroyan from further pounding[17]) in a match broadcast by ABC television's Wide World of Sports,[18] preparing for which he quit his regular job,[10] and dispatched of Duane Bobick, which took the latter's corner five minutes to bring him back into consciousness.

Fighting Bobick to make it to the national team, Lyle was behind on judges' scorecards, and when he fought Saroyan, he again was behind on points, which nonetheless didn't stop him from knocking out both.

On January 25, 1971, Lyle fought his last fight as an amateur, knocking out the Pacific Northwest Golden Gloves heavyweight champion Jim Wahlberg.

Meanwhile, two world's top-ranked heavyweights, Muhammad Ali and Joe Frazier, were preparing themselves for the Fight of the Century.

His amateur career outside of prison lasted only 14 months, during which he compiled a record of 25–4[21] (no stoppages,) with 17 knockouts at national and international contests.

[25] Lyle was an obvious choice for the 1971 Pan American Games and the 1972 Olympics, but as he stepped into the pro ranks, Duane Bobick, whom he knocked out twice, was set to represent the United States.

"[26] After he turned pro, Lyle visited his fellow inmates in prison the day before or after each and every professional fight.

[27] After dispatching of Buster Mathis, Lyle stated that he is looking for a match-up versus current undisputed champion Joe Frazier, saying "When I'm ready.

Yancey Durham, Frazier's manager and an interested observer, did compliment Lyle on his punching power.

[25] Lyle's undefeated streak ended on a one-sided decision to veteran Jerry Quarry: the latter gave one of his career best performances using a boxer/puncher style to create openings first, gaining the initiative using his greater experience.

Though in danger of falling too far behind on points, Ali appeared to be in control of the pace of the fight, and picked his moments to score.

Lyle, Muhammad Ali and Jimmy Young are the only boxers to have ever knocked down Foreman during a professional boxing match.

[30] Lyle scored impressive victories over rated José Luis García, and big names Oscar Bonavena and Earnie Shavers during his career.

[31] He also won a split decision over Joe Bugner, boring in with a thudding body attack in a fine contest.

[33] According to George Foreman, Ron Lyle was one of the three hardest punchers he had faced in his career along with Gerry Cooney and Cleveland Williams.

Draws with fringe contenders Stan Ward and Scott LeDoux were followed by a stunning one-punch loss to unheard-of Lynn Ball.

Ron retired again after a first-round knockout loss to then-rising star and undefeated power-hitting Gerry Cooney.

[37] He was the former trainer of light welterweight contender Victor Ortíz, who fought out of Denver during some of his amateur career.

[41] A biography titled Off the Ropes: the Ron Lyle Story was written by Candace Toft and released in the United Kingdom by Scratching Shed Publishing in May 2010.

[43] Ron Lyle appeared in the film Facing Ali,[44] a 2009 documentary, where he discusses his life and career.