MARTINEZ, Calif., Aug. 13 (San Francisco News Online) — Marcos Eduardo Iriarte-Valdez, 36, has been charged with murder in the fatal stabbing of Todd Stewart, 68, in Martinez, California, according to the Contra Costa County District Attorney’s Office and Martinez police. Iriarte-Valdez pleaded not guilty at an Aug. 12 arraignment in Contra Costa County Superior Court.
Prosecutors allege that Stewart encountered a person during an attempted burglary near his home on Aug. 6 and that the person fled after stabbing him. Stewart died from his injuries, police said.
The case has drawn attention because Iriarte-Valdez had been released from custody the day before the killing while facing separate burglary allegations. The charge remains an accusation. Iriarte-Valdez is presumed innocent unless prosecutors prove the case in court.
What happened before the killing?
Court records and Martinez police accounts show that Iriarte-Valdez was facing cases tied to alleged residential burglaries in Orinda on April 29. He was initially released in that case in May, according to court records.
Police took him into custody again on Aug. 4. Authorities said he allegedly violated a condition requiring home detention and electronic monitoring.
On Aug. 5, a judge released Iriarte-Valdez on his own recognizance and referred him back to home detention, according to court records and police. Release on one’s own recognizance means a person is released without paying bail but agrees to follow court orders and return for future hearings.
Martinez Police Chief Andrew White said the monitoring equipment apparently was not placed on Iriarte-Valdez until after Stewart’s death, according to reports citing the chief. The supplied records do not include the written release order or explain why the equipment was not in place sooner.
What do prosecutors allege?
Martinez police said Stewart was stabbed shortly after 5 p.m. Aug. 6 near his residence on Francis Court. Prosecutors allege the killing happened during or immediately after a burglary.
The murder case includes an allegation tied to the use of a deadly weapon and an allegation that the offense occurred while Iriarte-Valdez was released on bail or his own recognizance, according to information attributed to prosecutors. Those allegations could affect the case if they are proven, but they are not findings of guilt.
Police arrested Iriarte-Valdez at his home on Aug. 7, authorities said. The sources reviewed for this report do not include a probable-cause affidavit, an autopsy report or a detailed account of the evidence against him.
What is the status of the case?
Iriarte-Valdez entered a not-guilty plea at his arraignment. The case is pending in Contra Costa County Superior Court, and several reports identified Sept. 1 as a date for setting a preliminary-hearing schedule. One local report listed a different date, so the next hearing should be confirmed through the court docket.
The available reports also conflict over whether Iriarte-Valdez is being held without bail or has bail set at $1.1 million. The court’s current custody record was not provided in the source material.
A preliminary hearing is a proceeding in which a judge decides whether prosecutors have presented enough evidence for the case to proceed. It is not a trial and does not determine guilt.
What role do immigration authorities play?
The Department of Homeland Security said it placed an immigration detainer on Iriarte-Valdez on Sept. 23, 2025. An immigration detainer is a request from federal immigration authorities asking a jail to notify them before releasing a person so they can seek custody under federal immigration law.
DHS described Iriarte-Valdez as being from Venezuela and said he also had Spanish citizenship. The supplied records do not independently establish his immigration status, and the sources use varying versions of his full name.
An immigration detainer is separate from the state murder prosecution. The state case concerns the alleged stabbing and burglary-related conduct. Any federal immigration action would be handled separately by federal authorities.
The alleged homicide occurred in Martinez, in Contra Costa County, rather than San Francisco. The case is locally significant across the Bay Area because it involves Martinez police, Contra Costa prosecutors and courts, earlier allegations in nearby Orinda, and federal immigration authorities.
