In December 2004, Delgado became the Organized Crime Unit's special prosecutor, supervising and overseeing investigations into money laundering and defrauding the Public Treasury.

[1] In November 2016, a former agent of the United States Drug Enforcement Administration (DEA) revealed acusations of Delgado helping the Texis Cartel smuggle cocaine and weapons from El Salvador to Honduras.

[6] In 2020, he was the defense attorney for Mauricio Arriaza Chicas, the incumbent director of the National Civil Police, during an investigation into his role in the 2020 Salvadoran political crisis.

[5] A 2021 investigation conducted by journalist Héctor Silva found that Delgado had worked for Alba Petróleos de El Salvador, a subsidiary of the Venezuelan oil company PDVSA, in 2019, during which, he earned US$46,600.

[8] On 1 May 2021, the 13th session of the Legislative Assembly assumed office, and the Nuevas Ideas-led legislature voted to remove five justices of the Supreme Court and Attorney General Raúl Melara.

[10][11][12] Two weeks later, Delgado appointed Carlos Rodolfo Linares Ascencio, a trial judge from the Santa Ana Department, as his assistant attorney general.

[15][16] In December 2022, a video published on Facebook falsely claimed that United States President Joe Biden ordered the removal of Delgado from office.

[20] On 28 November 2023, Bukele publicly asked Delgado to investigate his entire cabinet, stating that he wanted to leave a positive legacy of combatting corruption.