The man charged with killing 68-year-old Todd Stewart had been released from custody one day before the fatal Martinez attack.
MARTINEZ, CA — A 36-year-old California man identified by federal immigration authorities as a non-U.S. citizen has pleaded not guilty to murdering a 68-year-old retiree during an alleged residential burglary, a case drawing scrutiny because the defendant had been released from custody one day before the killing.
Contra Costa County prosecutors charged Marcos Eduardo Iriarte-Valdez of Martinez with murder in the Aug. 6 death of Todd Stewart. The criminal complaint includes allegations that the killing occurred during a burglary, that Iriarte-Valdez personally used a knife and that he committed the offense while on conditional release in a separate burglary case. Judge David Goldstein ordered Iriarte-Valdez held without bail after his arraignment Wednesday.
Prosecutors allege Iriarte-Valdez stabbed Stewart at about 5:10 p.m. Aug. 6 while committing a residential burglary in Martinez. Police said surveillance video and other evidence helped investigators identify a suspect, and officers arrested Iriarte-Valdez the following evening. Authorities have said they knew of no prior connection between Stewart and Iriarte-Valdez.
The timing of the killing has focused attention on Iriarte-Valdez’s earlier criminal case. Police said he had been on pretrial release in connection with residential burglaries in Orinda from April. He was taken back into custody in early August after allegedly violating a home-detention monitoring requirement but was released on his own recognizance Aug. 5 and referred back to electronic monitoring. Stewart was killed the next day.
The Contra Costa County District Attorney’s Office said Iriarte-Valdez was out of custody on court-ordered electronic monitoring at the time of the killing. Martinez Police Chief Andrew White told local news organizations that the monitoring equipment apparently had not been placed back on Iriarte-Valdez before Stewart was killed. The circumstances surrounding his release have prompted criticism from some residents and renewed debate over how courts balance public safety with the rights of defendants who have not been convicted.
The case has also entered the national immigration debate. The U.S. Department of Homeland Security described Iriarte-Valdez as a Venezuelan national with Spanish citizenship who was unlawfully in the United States and said U.S. Immigration and Customs Enforcement had placed a detainer on him. ABC7 reported that federal officials identified him as a non-U.S. citizen but did not answer the station’s questions seeking clarification about his immigration history and current legal status. The San Francisco Chronicle likewise reported that his precise immigration status remained unclear.
Those distinctions matter because federal immigration classifications can involve questions about admission, visas, prior immigration proceedings and other records that have not all been made public in this case. State prosecutors have charged Iriarte-Valdez under California criminal law, and his immigration status is separate from whether prosecutors can prove the murder allegations against him. He has pleaded not guilty and denied the enhancements filed with the charge.
Stewart was a retired engineer who had lived in his neighborhood for decades, according to local reporting. Neighbors described him as a family man who enjoyed golf and had recently been spending more time traveling with his wife after retirement. He is survived by his wife and two daughters. A family friend told ABC7 that Stewart was a devoted husband and father who was active in his church community.
Police credited surveillance footage, license-plate recognition technology, physical evidence and community tips with helping investigators locate Iriarte-Valdez. The District Attorney’s Office said evidence in the investigation was also processed by the Contra Costa County Sheriff’s Office Crime Lab. Prosecutors filed the murder complaint Aug. 11 after Martinez police presented the case for review.
The complaint carries a special-circumstance allegation that the killing happened while Iriarte-Valdez was committing, attempting or fleeing a burglary. Prosecutors said that allegation, if proved to a jury, could make him eligible for life in prison without the possibility of parole. District Attorney Diana Becton said her office would pursue the case while offering assistance to Stewart’s family and the broader community.
Iriarte-Valdez remains in custody without bail. The District Attorney’s Office said the case is scheduled to return to court Sept. 9 before Judge Michael Nieto in Richmond to set a preliminary hearing date. The allegations have not been proved, and Iriarte-Valdez is presumed innocent unless convicted.
Author note: Last updated August 13, 2026.