The Colorado Court of Appeals Thursday affirmed the sentence for the ringleader in the killings of a teenager and his grandparents in Guffey on New Year's Eve in 2000.
Simon Sue, who pleaded guilty to three counts of conspiracy to commit murder and one count of involvement with organized crime, had argued his 53-year prison sentence was too harsh.
A three-judge panel of the appeals court said Sue's sentence was below the maximum allowed by law.
Sue was appealing a 2005 ruling by a state judge rejecting his request to withdraw his guilty plea.
Prosecutors said Sue ordered the killings of 15-year-old Tony Dutcher and his grandparents, Carl and JoAnna Dutcher, to ensure loyalty to a secret group.
Isaac Grimes was sentenced to 60 years in prison and Jonathan Matheny is serving a 66-year prison term for their roles in the killings.