Arrest Made in 2005 Homicide Case


(OXNARD, Calif) – On Wednesday, March 16, 2016, investigators from the Oxnard Police Department’s Major Crimes Unit arrested 31 year old Isaac Sinsun for the 2005 murder of Joaquin Castaneda. On November 13, 2005 at 6:55 p.m., officers from the Oxnard Police Department responded to a call of a gunshot victim in the 900 block of Richmond Avenue.  Officers arrived on scene at 7:01 p.m. and found the victim, Joaquin Castaneda, lying on the asphalt roadway suffering from a gunshot wound to the head. It was later determined that Castaneda had been shot in the face.
Oxnard Police Department Major Crimes Investigators, and forensic scientists from the Ventura County Sheriff’s Department Crime Laboratory, began an exhaustive investigation of the scene. Due to their diligent efforts, several critical pieces of evidence were located and recovered. The investigation at the scene revealed that Castaneda had likely been killed during a robbery.
The circumstances of Castaneda’s murder were very similar to a series of robberies that had been taking place in the City of Oxnard that same week. Oxnard Police Department Robbery Investigators teamed up with Major Crimes Investigators to work towards solving the cases in order to apprehend the individual(s) responsible for these crimes.  Information about these cases and their possible relationship was disseminated to all patrol officers in the city.
While on routine patrol, two patrol officers noticed a parked vehicle that matched the description of a suspect vehicle from the robbery series. These officers notified investigators, who responded to the scene. The investigators contacted several individuals associated with this vehicle. One of these individuals was Isaac Sinsun. Investigators focused on these individuals as possible suspects in the robbery series and the Castaneda murder. Detectives secured several search warrants for their residences and other locations associated with them.  Additional evidence was collected at these locations. Many of the recovered items of evidence were sent to the Ventura County Sheriff’s Department Crime Laboratory for examination and analysis. Additional items of evidence were sent to the California Department of Justice Crime Laboratory. These forensic scientists conducted examinations in the areas of DNA, trace evidence, fingerprints, ballistics, blood spatter, shoeprints, tire impressions, and handwriting comparisons. Through the years, detectives and the forensic scientists continued to work together to utilize all advances in forensic technology and testing to further the information gathered from the seized evidence.
Over the past ten years, Oxnard Police Department Major Crimes Investigators pursued all leads in this case, which lead to the discovery of additional evidence. In addition to the forensic examinations of the evidence, detectives conducted numerous interviews, employed undercover surveillance, and utilized digital forensics to investigate this murder. Oxnard Police Department Investigators worked cohesively with deputies and detectives from the Ventura County Sheriff’s Department, and with investigators from the Ventura County District Attorney’s Office, many times over the years on this investigation. The teamwork, perseverance, determination, and unwavering drive for justice, ultimately culminated in the Ventura County District Attorney filing the charge of murder against Isaac Sinsun for the homicide of Joaquin Castaneda. This case is continuing to evolve.  Additional arrests in this case are expected.
Investigators are encouraging anyone with information about this incident to contact Detective Jeff Kay at (805) 385-8174.  If you wish to remain anonymous you can call the Violent Crimes Hotline at (805) 982-7070 or Ventura County Crime Stoppers at (800) 222-8477.  You can also visit  to submit a tip via text or email.



Isaac Sinsun

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