MARTINEZ, Calif., Aug. 13 (San Francisco News Online) — Marcos Eduardo Iriarte-Valdez, 36, has been charged in Contra Costa County Superior Court with murder in the fatal stabbing of 68-year-old Todd Stewart in Martinez, prosecutors said. Iriarte-Valdez pleaded not guilty at an Aug. 12 arraignment.
The case has drawn attention to the timing of Iriarte-Valdez’s release from custody. Martinez police said he was released on his own recognizance Aug. 5, one day before Stewart was killed. He had been arrested Aug. 4 for allegedly violating a home-detention monitoring condition in a separate burglary case.
What prosecutors allege
Stewart was fatally stabbed shortly after 5 p.m. Aug. 6 near his home on Francis Court, according to Martinez police and the Contra Costa County District Attorney’s Office.
Prosecutors allege that Stewart encountered a person during an attempted burglary at or near his residence. The person then fled and stabbed Stewart, prosecutors allege. The murder case includes an allegation that the killing occurred during or immediately after a burglary. Prosecutors also allege that a deadly weapon was used.
Iriarte-Valdez was arrested at his home Aug. 7, Martinez police said. The charge and allegations have not been proved in court. Iriarte-Valdez is presumed innocent unless he is convicted.
Why the earlier release matters
Before Stewart’s death, Iriarte-Valdez was facing cases involving alleged 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 later placed under home detention. After the Aug. 4 arrest for an alleged monitoring violation, a judge released him the next day on his own recognizance and referred him back to home detention.
Home detention is a court-ordered restriction that requires a person to remain at an approved residence except for authorized activities. Electronic monitoring may be used to check compliance. Martinez Police Chief Andrew White said the monitoring equipment apparently was not placed on Iriarte-Valdez until after Stewart’s death.
At the earlier release hearing, Judge David Goldstein referred to a “risk to public safety,” according to the court account reported by the San Francisco Chronicle. The available information does not include the written release order or a full explanation of the judge’s decision.
What is known about immigration proceedings
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 local or state agency to notify them before releasing someone from custody and, in some cases, to hold the person briefly so federal officials can take custody.
DHS described Iriarte-Valdez as being from Venezuela and said he also had Spanish citizenship. The available records summarized in this case do not independently establish his immigration status. Immigration proceedings are separate from the California murder case.
What happens next
The murder prosecution will proceed in Contra Costa County Superior Court. A preliminary hearing would allow a judge to decide whether prosecutors have presented enough evidence for the case to continue toward trial. The available accounts give conflicting information about the next court date and about whether bail is set or denied, so those details are not included here.
The case concerns events in Martinez and the earlier burglary allegations in nearby Orinda. It involves the Martinez Police Department, the Contra Costa County District Attorney’s Office, the county courts and federal immigration authorities.
