First, I assume that by, "state trooper," you mean "California Highway Patrol Officer" (CHP).
In court, a witness must testify from personal knowledge -- unless the person is qualified by the court as an expert witness, on the subject of their testimony. So, you can object to the officer's testimony, e.g.: "Objection: Your honor, the witness stating a personal opinion, but he/she is not qualified as an expert by the court; moreover, as the officer was not present at the scene of the alleged violation, the officer is not testifying from personal knowledge."
And, if the judge starts asking the officer questions in an attempt to qualify the officer as an expert witness, then you can object again: "Objection: Your honor, by your conducting a voir dire of the witness's qualifications to testify as an expert, the court is engaged in aiding the prosecution of this matter."
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