SAN MATEO COUNTY, Calif. (KRON) — A murder case that went cold 30 years ago has now been closed, according to a press release from the San Mateo County Sheriff’s Office.
On July 7, 1992 Juliette Rivera, 25, of Alameda, was reported missing to the Alameda Police Department. APD opened a missing person investigation. At the time, investigators with APD spoke with Gregory Marc Riviera, 50, also of Alameda, who was an acquaintance of Rivera’s. Investigators found “numerous inconsistencies” in the statement that Riviera provided, and they began to suspect him of being involved in Rivera’s disappearance, according to the release.
Ten days later on July 17, 1992, the decomposed body of a young female was found by a farm worker in a rural area of unincorporated San Mateo County’s South Coast area. Later authorities identified the body as Rivera. An autopsy revealed that Rivera suffered blunt force trauma to the head from a flat object.
On August 7, 1992 SMC Sheriff’s Detectives issued a warrant for Riviera in San Mateo County, he was also charged with the murder of Rivera. Rivera fled his apartment around July 29, 1992 and avoided law enforcement for 30 years.
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In May of this year the Merced County Coroner’s Office contacted the SMC Sheriff’s Office about a local unhoused man known as “Jon Paul” who died on January 29, 2022. The coroner completed a fingerprint analysis to locate next of kin, and results matched Abraham Rivera, also known as Gregory Marc Riviera. It was then that the MCCO found the warrant for Riviera’s arrest in San Mateo County.
After further investigation, SMC Sheriff’s Detectives found that Gregory Riviera had a brother named John Paul. John Paul’s daughter confirmed to MCCO that John Paul was still alive and suffering from medical issues. She also told MCCO that her Gregory and John Paul had used one another’s identities for 30 years to evade law enforcement.
Since SMC Sheriff’s Office confirmed the identity of the deceased man as Gregory Marc Riviera, the case is now considered closed. This is just one of the many cold cases being handled in San Mateo County.
The SMC Sheriff’s Office has a Cold Case Unit as part of the Investigations Bureau. The Unit assists SMC Sheriff’s Detectives by reexamining cases that were once considered “unsolvable.”