MARTINEZ, Calif., Aug. 13 (San Francisco News Online) — Marcos Eduardo Iriarte-Valdez, 36, has been charged in Contra Costa County Superior Court with murdering Todd Stewart, 68, in Martinez. The Contra Costa County District Attorney’s Office alleges that Stewart encountered a person during an attempted burglary near his home before he was fatally stabbed.
Iriarte-Valdez pleaded not guilty at his Aug. 12 arraignment. The charge is an allegation, and the case has not been decided in court.
What happened in Martinez?
Martinez police said Stewart was stabbed near his home on Francis Court shortly after 5 p.m. Aug. 6, 2026. Police arrested Iriarte-Valdez at his home the next day.
Prosecutors allege the killing happened during or immediately after a burglary. The murder case also includes allegations that a deadly weapon was used and that the crime occurred while Iriarte-Valdez was released in another case.
The sources available for this report do not include a police affidavit, autopsy report or detailed account of the evidence. Police and prosecutors have not publicly established a motive or described any known relationship between Stewart and Iriarte-Valdez.
Why did the release become part of the case?
Before Stewart’s death, Iriarte-Valdez was facing allegations involving residential burglaries in Orinda on April 29, according to court records and Martinez police. He was initially released in that case in May.
Police said he was taken into custody Aug. 4 for allegedly violating a home-detention monitoring condition. On Aug. 5, a judge released him on his own recognizance and referred him back to home detention, according to court records and police information.
“Own recognizance” release means a person is released without posting bail after promising to return to court and follow specified conditions. Home detention can require a person to remain at a residence and comply with electronic monitoring or other court rules.
Martinez Police Chief Andrew White said the monitoring equipment apparently was not placed on Iriarte-Valdez until after Stewart was killed. The available records do not include the written order explaining the Aug. 5 release or the reason for the court’s decision.
What do immigration authorities say?
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 that a local or state agency notify them before releasing a person from custody and hold that person for a limited period, subject to legal requirements.
DHS described Iriarte-Valdez as being from Venezuela and said he also has Spanish citizenship. Those details and his immigration status are based on the department’s statements; the available court materials do not independently establish them.
An immigration detainer does not determine whether a person is guilty of a criminal charge. The murder case remains in state court, while any immigration proceedings would be separate.
What happens next?
Iriarte-Valdez remains in the Contra Costa County criminal case. Reports differ on whether the court has ordered him held without bail or listed bail at $1.1 million, so his precise custody terms could not be confirmed from the available records.
A further court appearance was reported for Sept. 1 to set a date for a preliminary hearing. At a preliminary hearing, a judge decides whether prosecutors have presented enough evidence for the case to proceed toward trial. That hearing does not determine guilt.
The earlier burglary allegations also remain unresolved unless and until they are decided in court.
