A non-party is a person who is not a named party in the lawsuit. He is neither the plaintiff nor defendant, and he does not have an interest in the lawsuit.
Upon service of a deposition subpoena, a non-party may not have to appear. Depending on the non-party’s involvement and knowledge of the case matter, the non-party may get a protective order to prevent his deposition.
Generally, a non-party may move for a protective order to prevent the taking of his deposition. The non-party may assert that the deposition is harassing, embarrassing and/or non-essential because of his relationship with the named parties or because other more knowledgeable parties are being deposed.
Further, there are evidence code privileges that may prevent depositions. Such privileges include the martial privilege, doctor-patient privilege, clergy-priest privilege, and attorney-client privilege.
Unfortunately, you will have to give a deposition when your protective order is denied. If you do not show up to the deposition, then you may be sanctioned or held to be at contempt of court.
However, you may have a lawyer present at your deposition. The lawyer will make sure the deponent is only asking relevant questions with in the scope of discovery.