Legal Question in Constitutional Law in California

Re: Confidental Informant

The answer depends upon the facts of each case, but usually the informant does not take the stand. Police don't "sit in" for the informant, either. The informant is usually not necessary at trial at all.

The informant's role in most cases is limited to telling the police who has committed a given crime so that they can start an investigation. They then begin gathering evidence which can be used at trial. If they find enough evidence to make their case, then they arrest the suspect and use that evidence against him at his trial. The informant's own statements and observations play no part in the prosecution's case, so there is no need for him to testify.

It is sometimes possible to find out who the informant is if the defendant has a plausible argument that he has been set up; if it turns out that the informant is someone who is biased against defendant, that fact will be helpful to the defense. Merely claiming that the informant must be someone who dislikes the defendant isn't enough, since that has nothing to do with whether the defendant is actually guilty.