I recommend getting your son the best criminal defense attorney possible and let that attorney evaluate the strengths and weaknesses of the state's case before addressing speedy trial issues.
These are obviously serious charges. Your son needs to retain a lawyer asap. Just because your son is not accused of being the "shooter" doesn't mean he can't be charged with and found guilty of murder. There are likely many more issues to be settled before you should be thinking about filing a speedy trial motion. Get him a lawyer.
My answer depends in part on whether your son is currently in jail. If my client is not sitting in jail, then I rarely ask for speedy trial. Time can be a criminal defendant's best friend in many cases. I perform my investigation as soon as possible. However, I've had cases where evidence gets lost, police officers get removed from the force, or witnesses move away and can't be reached. That is not to say that is what's going to happen in this case. If he is sitting in jail, then it does not hurt to ask for a speedy trial in most cases. Having said that, what you and I consider speedy and what the court considers speedy are two different things. The denial of the right to a speedy charge can lead to a dismissal. However, that is a rare case. The court is faced with a backlog of cases, not enough terms of court, and not enough of a budget to add terms of court.
This response is for informational purposes and is not intended to convey detailed legal advice on specific issues. Transmission of the information contained in this response is not intended to create, and receipt does not constitute, an attorney-client relationship. The attorneys of Futeral & Nelson, LLC practice law only in jurisdictions we are properly authorized to do so and do not seek to represent anyone in any other jurisdiction where this site does not comply with applicable laws and bar rules. This site does not make use of any secure encryption technology, and any transmissions to the law firm of Futeral & Nelson, LLC may be intercepted by third-parties. DO NOT send us any information that you regard as privileged or confidential. The lawyers of the Futeral & Nelson, LLC are licensed to practice law in the State of South Carolina. Readers should not act upon the information contained in this site or the linked sites without first seeking the advice of an attorney licensed to practice in your area.
It sounds like the best course of action at the moment is not a speedy trial but rather a thorough investigation in your sons defense. Essentially your are asking for an alibi defense at the moment which has to be disclosed to the prosecution 10 days before trial. It also means that someone will have to testify to that alibi.
In South Carolina you do not have to be the person to actually pull the trigger to be guilty of the crime under "accomplice liability" otherwise known as "the hand-of-one is the hand of all." So the fact that police said your son was not the shooter does not automatically result in the charges going away, it could mean that they believe he is an accomplice in someway and that there is an additional co-defendant(s) involved.