ADA Morales says that they cannot refile charges against Cesar Vargas after the judge dismissed the charges due to insufficient evidence. However jeopardy had not yet attached to Vargas' case, in a jury trial jeopardy attaches when the jury is empaneled and sworn in. Fernando Ramirez was murdered during a pre-trial hearing to determine whether the state had sufficient evidence to bind Vargas over for a trial by jury, Morales even said as much during his opening statement just seconds before the judge's law clerk got the call notifying the judge about Fernando being killed. The process of jury selection doesn't start until the judge rules that the prosecution has sufficient evidence to go to trial, and once that happens there can be as much as a few weeks in between starting the jury selection process and the jury being selected and sworn in. So this case was nowhere near having jeopardy attach to it. If/when additional evidence was found tying Vargas to the murder of Detective Winters and the Alcazar family, Morales would of been free to rearrest Vargas and refile murder charges against him.
The actor playing Fernando, the Mexican national, was NOT a native Spanish speaker.