Brandon Mumma allegedly moved his girlfriend's body into a narrow, locked space between two buildings in Lakewood, Colorado, after she died under suspicious circumstances, then discarded her belongings to avoid detection by police, according to prosecutors.
Background
Jax Gratton was last seen alive on April 15, 2025, when she left her apartment wearing a specific set of clothes that would later be found on her remains. Her roommate reported her missing after she failed to return home. For weeks, Gratton's family searched the Denver metro area for any sign of her whereabouts.
According to prosecutors, Mumma and Gratton were in a consensual intimate relationship at the time of her disappearance. Surveillance footage and cell phone data would later become central to the investigation into what happened that night.
On June 6, 2025, Gratton's body was discovered between buildings at 9655 and 9699 West Colfax Avenue in Lakewood—a narrow, 4-foot-wide space locked from both ends with a solid gate obscuring it from public view. The building at 9699 W. Colfax Avenue was vacant at the time.
The Investigation
The First Judicial District Attorney's Office announced Mumma's indictment in March 2026, charging him with one count of tampering with a deceased human body and one count of tampering with evidence. He appeared in court last week and entered a plea of not guilty.
Prosecutors allege that Gratton's last active phone session occurred in the early morning hours of April 16, 2025, using an IP address associated with 9655 West Colfax Avenue in Lakewood—Mumma's residence. Surveillance video allegedly captured Mumma entering the unit at approximately 5:55 a.m. on April 16.
"He remained inside until 6:57 a.m., when he moved his vehicle to the north side of the building," the DA's office stated. "Mumma then entered the building and returned with trash bags, which he threw into a dumpster."
A male friend arrived at Mumma's unit at 12:14 a.m. on April 16 and departed with Mumma at 1:43 a.m., leaving Gratton "alone and asleep under the influence of drugs," according to prosecutors. When police searched the unit on May 29, 2025, they found that furniture from April had been removed and none of Gratton's personal belongings—including her cell phone—were ever recovered.
Gratton was found lying on her side between the buildings with an air conditioning unit grate covering her lower body. A significant dent was noted on top of the air conditioning unit located directly below a second-story window of 9655 W. Colfax Avenue, Unit G—the same unit Mumma was seen entering with Gratton.
According to prosecutors, Mumma told police that Gratton was under the influence of gamma-hydroxybutyrate (GHB) and took too much that night. He claimed she passed out, began snoring, then made gurgling noises and vomited. Mumma alleged he rolled her onto her side before leaving with his male friend.
Gratton's autopsy report revealed no defensive wounds and no clear evidence of pressure on the neck leading to death, though strangulation could not be ruled out. Aspiration may have caused or contributed to her death. Toxicology detected methamphetamine, THC, citalopram, and trazodone in her system, but a drug overdose could neither be proven nor ruled out.
Investigators later classified Gratton's death as a "suspicious death."
Key Takeaways
- Brandon Mumma, 41, has been charged with tampering with a deceased human body and tampering with evidence
- Jax Gratton's body was discovered June 6, 2025, in a narrow 4-foot-wide space between locked buildings at West Colfax Avenue in Lakewood
- Surveillance footage allegedly shows Mumma entering his unit at 5:55 a.m. on April 16 and moving trash bags to a dumpster less than two hours later
- Gratton's phone and personal belongings were never recovered; furniture was removed from the unit by May 29, 2025
- Autopsy could not determine cause of death with certainty—strangulation and drug overdose both remain possibilities
What's Next
Mumma is due back in court on July 30. He is scheduled to go on trial in November. The case remains under investigation by Lakewood police.