Legal Question in Criminal Law in California

It depends on the nature of the case and what you mean by "separate." Criminal defendants are tried together all of the time if their is a common nexus of facts or if the crime by definition involves more than one culpable individual, as in the case of, for example, accessory liability, aiding and abetting, conspiracy, racketeering etc.

Yes.

the only proper advice is:

When questioned, arrested or charged with any crime, the proper questions are, can any evidence obtained in a test, search or statement be used against you, can you be convicted, and what can you do? A little free advice: exercise the 5th Amendment right to SHUT UP and do NOT talk to police or anyone about the case except with and through an attorney. If you don't know how to represent yourself effectively against an experienced prosecutor intending to convict, then hire an attorney who does, who will try to get a dismissal, charge reduction, diversion, programs, or other decent outcome through motions, plea bargain, or take it to trial if appropriate. If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me. I�ll be happy to help fight and get the best outcome possible, using whatever defenses and sympathies there may be.