A preliminary hearing is an evidentiary hearing in which the prosecution must provide to a court enough evidence to establish probable cause that a crime occurred and that the defendant is the perpetrator. The hearing is not entended to establish guilt and it's rest cannot be brought up by the prosecution during the guilt phase (jury trial).
At the PX, the court will either hold the defendant to answer for the crime, reduce the matter from a felony to a misdemeanor or dismiss the case outright - although the last option is very rare. In fact, even if the matter is dismissed, the DA would still be able to refile criminal charges on the matter. Good luck.
This is a conversation that you should be having with this person's attorney. My colleague indicated procedurally what will happen at a PH-with regards to the specifics the attorney is the best person to have this conversation with.
Sounds like the case you are referring to might be venued in San Bernardino County. I don't know which case you are talking about, however, San Bernardino County generally calls the cases Pre-Prelim and Prelim. In a pre-preliminary hearing, the purpose is to make sure that the witnesses in the case (such as the police officer, other witnesses etc) are available to testify, are under appropriate subpoena and that the parties are ready to proceed. It is more an interest in confirming with the court whether the parties are both "ready" to proceed to preliminary hearing. Oftentimes, officers may be unavailable, in training, sick, out of town, etc., so the pre-preliminary hearing confirms all of that. As far as the PH is concerned, that is a probable cause hearing to determine if there is enough "reasonable suspicion or probable cause" to believe a crime has been committed. There is no right to a jury in the PH. A judge will evaluate the facts and determine if the charges warrant being "held to answer" so that it can proceed towards jury trial.
A preliminary hearing is a hearing designed so a defendants time, energy, and expenses are not wasted on charges that are not likely to go to trial. A pre hearing is likely a setting.
Preliminary Hearings may be conducted pursuant to Prop 115. If so, the rules of evidence allow hearsay evidence at these hearings
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