West Valley City police say they have finally identified the primary suspect in Sheree Allen's death, found dead in a dumpster on Jan. 24, 2005 — but the man they say did it will never face a courtroom. Investigators named Carl “Big Smooth” Swanigan as the primary suspect in the investigation into Allen's strangling death, closing a case that sat unsolved for more than two decades.
According to KSL, DNA evidence linked Swanigan to Allen, and police say they had sufficient evidence and probable cause to identify him as the primary suspect in the strangling. The Salt Lake County District Attorney's Office reviewed the case and, per a letter dated Sept. 4, found probable cause to believe Swanigan was the primary suspect in Allen's murder. Prosecutors will not file charges, however, because Swanigan is deceased.
West Valley City police closed the case despite that lack of charges, a decision the department says was bolstered by the strength of the underlying work. As reported by KSL.com, the investigation received support from three separate reviews, including two independent experts who concurred with the police department's conclusions after examining the findings.
A Relationship Marked by Violence
Allen was Swanigan's girlfriend, and the station's report notes he was the last person known to have been with her before her death. Allen reportedly had facial injuries attributed to Swanigan, per a witness account, and detective John Wells has said domestic violence played a role in her death and that Swanigan made specific threats against Allen, as noted by KSL.com.
Wells was assigned to the case in 2023 and worked to eliminate other possible suspects as he dug back into the decades-old file. In 2024, he met with the Sherry Black Foundation, which connected him with the two independent experts who would go on to review the department's findings alongside prosecutors, KSL.com reported KSL.com.
A Mother's Long Wait for Answers
Sheree Allen's mother, Lillie Allen, said she waited 21 years for resolution in her daughter's case. Per a report from KSL.com, she thanked detectives for their efforts and said she appreciated the work it took to finally reach an answer, describing a mix of happiness, joy and gratitude now that the case has been resolved.
That relief is tempered by unfinished business. Lillie Allen expressed sadness that Swanigan died before facing justice for what investigators say he did. She said she knew Swanigan and his family, and that she had been unaware of any troubles between him and her daughter at the time — she said Sheree had been preparing to leave him.
A separate case-summary page from the Utah Bureau of Criminal Identification describes Allen as having been last seen alive by Swanigan and states that he gave an initial statement to investigators but refused to continue cooperating, according to the Utah Bureau of Criminal Identification. Two decades after Allen's body was found, the case now stands closed in the eyes of West Valley City police, even without a courtroom verdict to close it in the eyes of the law.
