Ramon Joseph Rivas admitted second-degree murder and multiple sentencing factors in the death of his girlfriend, Jessica Marie Tinoco.
VENTURA, Calif. — A murder prosecution that began with Ramon Joseph Rivas facing homicide and child-endangerment charges ended with a 51-years-to-life prison sentence after he admitted killing his girlfriend, Jessica Marie Tinoco, and accepted a series of allegations tied to the crime and his prior record.
The Aug. 7 sentence followed a May 20 guilty plea to second-degree murder in Ventura County Superior Court. The plea did more than resolve the homicide count. According to the Ventura County District Attorney’s Office, Rivas, 36, admitted using a deadly weapon, having a third strike, having a prior serious or violent felony and having a serious-felony prior. He also admitted aggravating factors stating that the crime involved great violence, Tinoco was particularly vulnerable, he had engaged in violent conduct, he had prior convictions and he had previously served a prison term. Prosecutors had announced before sentencing that the combined resolution exposed him to as much as 51 years to life.
The final sentence therefore capped a legal progression in which the case narrowed from disputed criminal charges to admitted criminal liability. When prosecutors first filed the case in October 2024, Rivas was accused of murder, child endangerment and strike-related allegations. He was held without bail while the case proceeded. More than a year and a half later, he changed course at an early disposition conference and entered the second-degree murder plea. Court reporting at the time said four child-endangerment counts remaining in the case were to be dismissed at sentencing. The plea avoided a murder trial while preserving a potential sentence measured in decades before any possibility of release.
The underlying crime occurred Sept. 27, 2024, at a Simi Valley residence shared by Rivas and the 34-year-old Tinoco. Prosecutors said police responded to a reported stabbing and encountered Rivas leaving the residence shirtless with blood on his upper torso. Officers detained him, went inside and found Tinoco just inside the front door with multiple wounds. A bent steak knife with blood on it was recovered from the living room floor. Authorities said Tinoco was taken to Los Robles Hospital and pronounced dead.
Witnesses described the attack as following a domestic dispute. According to the District Attorney’s Office, Rivas went to the kitchen, took a knife and attacked Tinoco as her children were present. Prosecutors said the children fled the residence and that Tinoco suffered multiple wounds, four of which were determined to be fatal. The office’s later releases said the stabbing occurred in front of all five children. Earlier police-based reporting said two of the children were present during the attack, including a daughter who called 911. The discrepancy concerns the number characterized as direct witnesses, not the central facts that children were in the home, fled and sought emergency help.
Those circumstances also shaped how prosecutors spoke about the plea. Senior Deputy District Attorney John Barrick, who handled the prosecution for the Major Crimes Homicide Unit, said in May that the children’s presence made the killing especially consequential. The prosecution’s public statement emphasized that a prison term could not reverse what they had witnessed. By the time of sentencing, Barrick said Rivas’ willingness to accept responsibility did not excuse the murder or what it had done to Tinoco’s family. The statements reflected the distinction between accepting a guilty plea as a legal resolution and treating that plea as an answer to the harm caused by the crime.
The sentencing allegations are significant because they form part of the adjudicated record, rather than remaining accusations. The official case summary identifies Penal Code section 187(a) for second-degree murder and lists a deadly-weapon allegation along with strike and serious-felony allegations. The prosecutor’s filing also cites California sentencing rules concerning great violence, vulnerability, prior convictions, prior imprisonment and violent conduct. The District Attorney’s Office did not publish a complete calculation assigning a specific portion of the 51-year minimum term to each admitted allegation. As a result, the reliable public record supports identifying the factors without speculating about a year-by-year formula that the sentencing release does not provide.
The guilty plea also changed how the September 2024 events could be described. In the first days after Tinoco’s death, authorities properly framed the case in terms of accusations: Rivas was accused of stabbing her during a domestic dispute, and prosecutors would have been required to prove the murder charge if the case went to trial. The May plea removed that uncertainty as to criminal responsibility. Rivas admitted second-degree murder. The August hearing then became a sentencing proceeding involving an admitted homicide rather than a trial over whether he had committed it.
The child-endangerment counts followed a more complicated procedural path. The original October 2024 announcement listed two counts, while later court reporting on the plea referred to four remaining counts scheduled for dismissal. The publicly available prosecution releases do not fully explain when or why the number changed. Rather than treating those counts as convictions, the record shows that the murder plea became the basis for the final judgment and that the additional child-endangerment charges were not the offenses for which Rivas received the Aug. 7 sentence.
The family was able to address the court before the final punishment was imposed. Tinoco’s daughters spoke about being inside the home, trying to respond to the violence and getting younger siblings to safety, according to courtroom reporting. Their statements supplied a human account of facts that appear more clinically in charging papers and prosecution releases. Rivas also addressed the family and expressed regret. He apologized to Tinoco’s children, but the court proceeded with the 51-years-to-life sentence contemplated as the maximum when he entered his plea.
The case also demonstrates why the prior-record allegations mattered procedurally. Prosecutors did not present Rivas as a person facing only the ordinary punishment associated with a single newly charged crime. His plea included an admission identified as a third strike and acknowledgments of a serious-felony history, prior convictions and a previous prison term. Those were not incidental biographical details added after the fact; they were among the formal allegations listed in the prosecution’s case information and admitted alongside the murder count. Their presence helped define the sentencing exposure announced months before the judge imposed the final term.
Still, the legal structure does not change the central loss in the case. Tinoco was a 34-year-old mother of five who died after being attacked in her own residence. Her children were forced to flee and seek help while the violence was unfolding. Local reporting following her death and at the sentencing documented the family’s grief, while the prosecution repeatedly emphasized the children’s experience as one of the defining facts of the case.
The Aug. 7 judgment completes the transition from accusation to conviction and sentence. Rivas is no longer awaiting trial or a determination of guilt; he stands convicted by his own plea of second-degree murder and has been ordered to serve 51 years to life in state prison. The District Attorney’s Office has not announced another major proceeding in the case, leaving the sentence as the final reported disposition of the prosecution arising from Tinoco’s September 2024 death.
Author note: Last updated September 21, 2026.