Photo: Isabel Bernal-Sanchez and Diego Hernandez-Antonia
Originally published as a Mammoth Lakes Police Department Facebook post –
“On April 5, 2022, the Mono County Superior Court sentenced Diego Hernandez-Antonia to a term of 11 years in state prison for the voluntary manslaughter of Isabel Bernal-Sanchez, closing one of the longest “cold cases” in Mono County history.
In Spring 2003, hikers discovered scattered human remains just north of the town of Mammoth Lakes. Initial investigation revealed the remains to be female however, the case went cold when no positive identification of the remains could be made.
Over the next 17 years, forensic technology, particularly DNA analysis, made rapid advances and in early 2020, the Mono County District Attorney’s Office submitted a DNA sample to be tested using recently developed technology which allowed a composite profile of the decedent to be created, including a detailed facial reconstruction.
In November of 2020, after releasing the composite to the media and public, a member of Isabel Bernal-Sanchez’s extended family came forward to speak to law enforcement about the possibility of the remains being Isabel’s. Family members immediately recognized the composite reconstruction as being Isabel. DNA samples from the reporting party as well as Isabel’s brother, living in Mexico, finally confirmed the remains as belonging to Isabel Bernal-Sanchez.
Isabel came from Mexico City to Mammoth Lakes in 2002 and worked as a housekeeper in Mammoth Lakes. Several months later, her boyfriend, Diego Hernandez-Antonia, also arrived in Mammoth Lakes, where they stayed with extended family. In the fall of 2002, Diego and Isabel went for a walk however, only Diego returned. When questioned later by family members, Diego said that Isabel had left the area with someone else and provided a forged note from Isabel telling her extended family not to look for her.
With the information provided by Isabel’s family, the Defendant was arrested on August 13, 2021, for the murder of Isabel Bernal-Sanchez. Initially, Diego Hernandez-Antonia stated that he had no idea who Isabel was. With further questioning, his story changed, and he admitted knowing Isabel, but said that they separated soon after going out on a “walk” in the fall of 2002.
Finally, he told investigators with the Mono County District Attorney’s Office that when he and Isabel went for a walk, they had climbed the hills over Shady Rest Park to build a rope swing, that Isabel had fallen off the rope swing and hit her head, and that he buried her body in a panic. This was contrary to much of the evidence that had been gathered.
Given the passage of time, issues within the case and after consultation with the family of Isabel, the People accepted a plea to voluntary manslaughter for the aggravated term of 11 years in state prison.
This case was prosecuted by Deputy District Attorney Tobias Hasler. This difficult, long-running case required the assistance of many people, and that a successful resolution was only possible due to their work.
To that end, the People would like to thank the Mono County Sheriff’s Office, the Mammoth Lakes Police Department, the California Department of Justice, the FBI, Stanislaus County Sheriff’s Office, Sacramento County Coroner’s Office, Othram Forensic Genealogy Lab, Investigators of the Mono County District Attorney’s Office, and most especially Isabel’s extended family. While this case involved high-tech forensics, it would not have been solved without the brave cooperation of these witnesses.”