Man arrested in Dubuque in relation to Colorado cold case

Police said a Dubuque man was arrested Monday morning on a homicide charge in connection with a Colorado cold case. 55-year-old Robert McClain was arrested on a warrant from Adams County, Colo. A press release from the Dubuque Police Department states, authorities in Dubuque received a tip suggesting McClain’s involvement in a Colorado cold case. This information was shared with the Thornton Police Department in Colorado, who led the investigation with support from Dubuque Police. Thornton Police Department officials said McClain’s arrest is related to the 2003 murder of 29-year-old Rosa Arguello. According to the Colorado Bureau of Investigation’s Cold Case Unit, Arguello’s body was found beside a road in the northern area of Thornton on Oct. 17, 2003. She had been stabbed multiple times. Thornton Police Department officials said arrangements are being made for McClain to be extradited to Colorado but declined to release additional information. McClain also has a local criminal history, which includes attempted murder in 2013, parole violation in 2020, and control of a firearm by a felon and public intoxication in 2024.