Gilmar was the police officer who returned Victoria Madsen to the hospital in the Season 1 episode Histories. He was portrayed by actor Larry Clarke.
When Victoria was returned, Gilmar claimed he had found her unconscious in the park. However, Victoria is tachycardic and the team think it is a new symptom. After thinking about it, House goes out to meet Gilmar, who sticks to his story. House notices that Gilmar is wearing a taser and notes that a taser strike would have caused the tachycardia. Gilmar sticks to his story and when House tries to bribe him, he just looks at House like he's crazy.
House goes back to Victoria's room and realizes that she suffered a taser strike on the thigh and she barely felt it. He tests her pain response in the same location and finds she's insensitive. This leads him to the correct diagnosis of rabies.