Legal Question in Criminal Law in California

Re: probable cause hearing

No.

Judges don't drop charges. Only prosecutors can do that.

A preliminary hearing (which is likely what you meant by a "probable cause hearing") is a test of the sufficiency of the prosecutor's evidence, not of the defendant's. If the prosecutor has evidence strong enough to potentially persuade reasonable jurors of the defendant's guilt, then it doesn't matter what contrary evidence the defendant may have. His evidence will matter at trial, but it won't at the prelim.

If the prosecutor doesn't have enough evidence at the prelim then some or all of the charges will be dismissed; this is not the same thing as "dropping" them and, more importantly, does not depend upon whether witnesses testify for the defense.

Even at trial, the witnesses will have to do more than just "show up". They will have to testify about an issue relevant to the defendant's guilt or innocense and will have to persuade the jury that there is at least a reasonable doubt.

Re: probable cause hearing

Anything is possible. IF the witnesses credibly establish a defense or alibi to the charges, then yes, charges might be dropped. You need counsel to make sure the witnesses are actually helpful, and they are presented well. Feel free to contact me if you want legal help in doing this right.