The boy died in May 2013 and his mother and her boyfriend were later convicted of torturing and murdering him. Evidence at trial indicated months of beatings and torture.
Prosecutors then went after the social workers with the Los Angeles County Department of Children and Family Services who were involved in his case, saying they failed to take appropriate steps to protect the boy and they falsified documents relating to his case.
Two social workers, Stefanie Rodriguez, 34, and Patricia Clement, 69, were charged along with two supervisors, Kevin Bom, 40, and Gregory Merritt, 64, with one felony count each of child abuse and falsifying public records.
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Prosecutors say the four minimized evidence of abuse and violated multiple policies, reporting that safety programs at Gabriel's home were working at the time abuse was escalating.
An autopsy report showed bruises, fractures, and cuts all over his body including his groin as well as BB's embedded in his body.
If the case had proceeded to trial and the defendants had been convicted, they could have faced over 10 years in prison.
But on Monday, a three-justice panel of the 2nd District Court of Appeal issued an opinion directing a lower court to dismiss the charges against the social workers.
In an 2-1 opinion, the panel concluded that there was no probable cause to hold the four on charges of child abuse and falsifying documents.
"We conclude that the petitioners never had the requisite duty to control the abusers and did not have care or custody of Gabriel for purposes of Penal Code section 273a, subdivision (a). We further conclude that the petitioners were not officers within the meaning of Government Code section 6200,'' wrote Justice Francis Rothschild.
"There is, therefore, no probable cause to hold them on charges of violating those laws and the trial court should have granted the motions to dismiss," the opinion continued.
In June 2018, Superior Court Judge George G. Lomeli sentenced Isauro Aguirre to death for the boy's first-degree murder and a special circumstance allegation of murder involving torture. Pearl Sinthia Fernandez was sentenced to life in prison without parole after pleading to first-degree murder and admitting the torture allegation.
Lomeli was also handling the social worker case and in 2018 had denied a motion to dismiss the charges, saying the boy's death was "foreseeable."
There was no immediate word on whether the Los Angeles County District Attorney's office plans to appeal the appellate court decision or further pursue the case.
City News Service contributed to this report.