You should consult an attorney immediately. If you cannot afford one, try to talk to his public defender. The DA is not required to give him an offer, but the attorney should try to talk to the judge to see if a deal can be reached.
I agree with both attorneys. If you and your son are not happy with the representation, the Judge will usually give you time to seek out your own lawyer. Many times however the DA will make an offer on the day of trial.
Your son has an attorney. Unless he is a minor, that means your son should be discussing his case with his attorney, including the nature of a plea and whether to offer one.
If he or you think you can afford private counsel, your son can contact the CA and county bar associations for referrals.
The foregoing is for general information purposes and does not establish an attorney-client relationship.
Something is missing. The DA ALWAYS offers some sort of a deal. It may be a good one or it may not be, depending on the evidence, but there are always offers discussed.
I don't know what the evidence is against him, but if the case is strong, he (and his attorney) may want to take a deal. If there are weaknesses in the case or the DA can't prove it, then it may be headed to trial.
The above answer is for general information only and is based on the information you posted. Every case is fact dependent, so to get a thorough analysis of your situation, you will need to consult face to face with an attorney licensed to practice in the jurisdiction where the incident took place. Do not conclusively rely on any information posted online when deciding what to do about your case.
My colleagues are correct- if your son is unhappy with his representation he should consider hiring a lawyer. Are you sure there was no plea offered or did he reject a prior offer? I agree that something is missing here.
I would get a second opinion. You may also want to talk to his attorney about hiring an investigator. Public Defender Offices have had major budget cuts and you can't just rely on the police reports.