The case has put a Bay Area pretrial-release decision and a federal immigration detainer at the center of a fatal-stabbing prosecution. Key facts, including the basis for the release decision and federal custody options, remain unresolved.
Marcos Iriarte-Valdez was charged in the fatal stabbing of Todd Stewart, 68, in Martinez, California, after a California judge released him one day before the alleged killing. Iriarte-Valdez had been in custody in a separate Contra Costa County burglary case, according to prosecutors and the Department of Homeland Security.
The case has become a flashpoint in the Bay Area because the Department of Homeland Security says it had lodged an immigration detainer on Iriarte-Valdez, while California officials say federal authorities retain the power to enforce federal immigration law. The murder charge remains an allegation, and the public record described so far leaves important questions about the release decision unanswered.
A release before the fatal attack
Contra Costa County prosecutors said Iriarte-Valdez had been charged in connection with burglaries at occupied homes in April. He was on pretrial release in that case when authorities arrested him Tuesday on an alleged violation of a home-detention condition.
He was then released on his own recognizance Wednesday, according to the account provided by prosecutors. Stewart was killed the following day, placing the timing of that release at the center of scrutiny.
Being released on one’s own recognizance generally means a defendant is allowed to leave custody without posting bail while promising to return to court and comply with conditions. It is not a finding that a person is innocent or guilty of the underlying allegations.
The available reporting does not identify the judge by name or fully detail the hearing record, the arguments made by prosecutors and defense counsel, or why the court concluded release was appropriate at that time.
The allegation in Martinez
Prosecutors allege Iriarte-Valdez fatally stabbed Stewart outside Stewart’s home in Martinez, a city in the East Bay. They say Stewart encountered him in a garage during an attempted burglary and that Iriarte-Valdez tried to flee before the stabbing.
Martinez police arrested Iriarte-Valdez on Friday evening in connection with Stewart’s death, according to the reported account. Investigators reportedly used community tips and automated license-plate-recognition technology to identify and locate him.
Prosecutors have charged him with murder and added allegations that the killing occurred during or immediately after a burglary, that a knife was used, and that the alleged offense occurred while he was released on bail or his own recognizance.
Those enhancements could affect the potential consequences if the allegations are proved in court. They are allegations by prosecutors, not findings by a judge or jury.
Stewart’s death shocks a neighborhood
Stewart was described as a 68-year-old retiree who had lived on his Martinez street for about four decades. The allegation that a fatal encounter took place at or near his home has intensified the local reaction to the case.
The circumstances also give the prosecution a factual narrative broader than a single violent incident: authorities are linking the homicide allegation to an attempted residential burglary and to earlier burglary charges in the county.
That connection will still need to be tested through the criminal process. The defense may challenge the evidence, the sequence of events, identification evidence, intent, or any other part of the prosecution’s account.
For Stewart’s family and neighbors, the immediate concern is the loss itself. For court and policy officials, the case raises a separate question about how pending charges, alleged supervision violations and public-safety risk are weighed before trial.
DHS presses its immigration argument
DHS said it placed an immigration detainer on Iriarte-Valdez on Sept. 23, 2025. The department said he was born in Venezuela and has Spanish citizenship, and that he had been legally admitted to the United States during the George W. Bush administration but was later classified by DHS as an undocumented immigrant.
An immigration detainer is a request from federal immigration authorities asking a local law-enforcement agency to notify the federal government before releasing a person and, in some circumstances, to hold the person for a limited additional period. A detainer does not itself decide a criminal case.
DHS used the case to criticize sanctuary policies, arguing that local cooperation with Immigration and Customs Enforcement can prevent people it identifies as removable from returning to the community. The department called for California to turn Iriarte-Valdez over to federal authorities after the murder allegation.
The federal agency’s position treats the case as evidence of a breakdown in coordination. But the available account does not establish whether federal officers sought custody at each stage of Iriarte-Valdez’s local criminal proceedings, whether a detainer was communicated to the court, or what legal and factual information was before the judge at the release hearing.
California disputes the blame
Gov. Gavin Newsom’s office said Iriarte-Valdez should face justice for the alleged crime. Diana Crofts-Pelayo, Newsom’s chief deputy director of communications, said nothing in California law stops federal authorities from enforcing federal immigration law.
Her statement rejected the premise that California was responsible for an ICE enforcement failure, saying the federal government has substantial resources to enforce its own laws. That response frames the dispute differently: not as a question of whether a local court should become a federal immigration enforcement arm, but whether federal agencies used their existing authority.
The conflict reflects a wider policy divide. Supporters of close local-federal cooperation argue that immigration detainers are a public-safety tool, especially when a person faces serious criminal allegations. Critics argue that state and local criminal courts must make custody decisions under state law and individual case facts rather than immigration status alone.
Neither position answers the narrower courtroom question: what information was available when Iriarte-Valdez was released and whether any release condition should have been changed or strengthened.
What the case will test next
The criminal case will determine whether prosecutors can prove the murder and related allegations beyond a reasonable doubt. Iriarte-Valdez is entitled to the presumption of innocence and to challenge the charges in court.
Separately, the release hearing may face deeper examination from court administrators, prosecutors, defense lawyers and elected officials. The most consequential facts may be procedural: the precise charges pending at the time, the claimed home-detention violation, the prosecution’s recommendation, the defense position and the court’s stated reasoning.
There is also an unresolved federal question. DHS has said it wants custody of Iriarte-Valdez, but any immigration proceedings would operate alongside, not replace, the California prosecution over Stewart’s death.
For now, the verified through line is stark: a defendant facing burglary allegations was released from local custody, and prosecutors say he was charged the next day in the fatal stabbing of a Martinez retiree. The legal system will now have to address both the homicide accusation and the decisions that preceded it.
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