The Civil Guard believes that Sánchez's former chief of staff in the PSOE collaborated "closely" with Leire Díez

The Central Operational Unit (UCO) of the Civil Guard targets Juan Manuel Serrano for a “relevant and preeminent participation” in the Leire case. He was head of cabinet for Pedro Sánchez at the PSOE from 2014 to 2018 – before he reached Moncloa – and president of Correos from 2018 to 2023.