The San Jose teenager accused of sexually assaulting his 2-year-old cousin before the toddler died will be facing fresh charges Monday: murder and “assault with a hair tie,” the Mercury News has learned.

The Santa Clara County District Attorney’s Office declined to explain the hair tie charge, but the grandmother of the toddler named Jaxon Juarez, who was in foster care with the teen’s family, told the Mercury News that she had seen a suspicious red line on his neck more than a week before his death. She said she had alerted a social worker.

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The Santa Clara County Medical Examiner, Dr. Michelle Jorden, has yet to release a cause of death.

Numerous questions have been raised since the child’s death, including whether the county’s child welfare agency that placed him with the teenager and his mother missed red flags in vetting the family and protecting Jaxon.

The new criminal charges are expected to be added during a hearing Monday in Santa Clara County juvenile court. Prosecutors are also expected to request that the case of the cousin, who turned 18 just days after Jaxon’s April 9 death, be moved to adult court. If convicted of murder as an adult, the teenager could face life in prison. If convicted in juvenile court, he faces up to 7 years in a secure facility at juvenile hall.

The Mercury News is not naming the teenager because he remains in juvenile court where identities are protected, nor naming his mother to also protect his identity.

Santa Clara County’s Department of Family and Children’s Services had placed Jaxon with the teenager’s 40-year-old mother about six weeks before Jaxon was found unresponsive in her home on April 5. Five days later, he was taken off life support and died.

The Mercury News learned last week that the woman, also considered Jaxon’s cousin, had been convicted in 2014 of felony child endangerment after drunk driving with her 1-year-old daughter in the back seat. Child welfare advocates said the conviction should have automatically disqualified the woman as a potential foster parent.

The county has declined to answer questions as to why she was chosen to care for Jaxon, or share any information about a possible ligature mark on Jaxon’s neck. The Mercury News has not independently verified the boy had such a mark.

In a statement Sunday, however, county spokesperson Peter Gallotta said the county is conducting a “comprehensive investigation” of the death, and that the state Department of Social Services is also conducting an independent review.

“We are working urgently to understand exactly what happened, and we remain committed to publicly sharing the results of our investigation, and the independent investigation being conducted by the State, when they are available and to the extent permitted by law,” Gallotta said.

Jaxon’s death came just as the California Department of Social Services was completing its 18-month oversight of the county’s child welfare agency, saying in a recent statement that the county had made many improvements to child safety since reforms began.

The state, as well as the Mercury News, had investigated the agency after the deaths of two children in its care: 3-month-old Phoenix Castro who died of a fentanyl overdose in her father’s home in 2023 after social workers said she wouldn’t be safe there, and 7-year-old Jordan Walker, who was stabbed allegedly by an uncle in 2024 after the county placed him with his grandmother, despite concerns from relatives he would be in danger there.