LOS ANGELES (CBSLA) — An emotional grandfather of Gabriel Fernandez took the stand Monday in Downtown L.A in the child’s murder case.

Robert Fernandez broke down several times during the testimony where he spoke about a custody battle that allowed the boy to move back in with his accused killers.

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The boy had lived with Fernandez and his late wife for nearly eight years and thought they had complete custody of him until the mother said he wanted him back.

The boy’s mother and her boyfriend eventually took Gabriel back and deputies told Fernandez their custody was not valid and the mother had the legal right to take her son back.

Prosecutors are seeking the death penalty against Isauro Aguirre, 37, who is charged in the May 22, 2013 death of Gabriel Fernandez. Pearl Sinthia Fernandez, 34, and the mother of Gabriel, will tried separately on similar charges.

Young Gabriel’s death triggered investigations into the county’s child welfare system and resulted in criminal charges of child abuse and falsifying public records being filed against two former county social workers and two of their supervisors.

As jury selection began late last month, Superior Court Judge George G. Lomeli said the boy “extensive internal and external injuries.”

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Lomeli said the trial is expected to last about six to eight weeks.

Los Angeles County Fire Department personnel were sent May 22, 2013, to a home in the 200 block of East Avenue Q-10 in response to a call that the boy was not breathing. He was declared brain dead that day, but not taken off life support until two days later.

The prosecution has alleged that the child suffered a fractured skull, several broken ribs and was burned over his body.

In court papers filed last year, Deputy District Attorney Jonathan Hatami wrote that a first-grade teacher made a report to authorities about Fernandez allegedly hitting her son with the metal part of a belt, causing injury.

“This was essentially the beginning of the eight months of torture and abuse of Gabriel Fernandez by Pearl Fernandez and Isauro Aguirre in Palmdale,” the prosecutor wrote, adding that the boy was “withheld from school by the defendants for the last three weeks before he was murdered.”

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