San Mateo County on Monday opened a 10-day administrative hearing that could make Sheriff Christina Corpus the first elected county sheriff in California to be removed from office. Retired Santa Clara County judge James Emerson is presiding over the proceeding, which follows the Board of Supervisors’ unanimous June vote to oust the first-term sheriff under powers granted by Measure A, a charter amendment approved by 84 % of voters in March. County attorneys argue that Corpus retaliated against critics, obstructed internal investigations, neglected her duties and maintained an undisclosed romantic relationship with her chief of staff, Victor Aenlle. In opening statements, county counsel Jan Little said the evidence would show a pattern of intimidation and abuse of authority detailed in a 400-page investigative report released last year. The county’s first witness, former Undersheriff Chris Hsiung, took the stand on the hearing’s opening day. Former Assistant Sheriff Jeffrey Kearnan later testified that he refused a role in Corpus’s leadership team after learning of her relationship with Aenlle, telling the tribunal, “If he’s in, I’m out.” Each side has up to five days to present evidence, after which Emerson will have 45 days to recommend whether cause exists for removal; the Board then has 30 days to issue a final decision.