If you get a subpoena, yes. A subpoena is a court order directing you to appear at a place and time to give sworn testimony. Other laws require that you testify truthfully or be prosecuted for perjury or held in contempt of court. Failure to obey a subpoena subjects you to the contempt process. You can ultimately be arrested and brought before the judge. You can also be incarcerated until you testify.
These things usually do not happen but they are certainly possible and I have seen them happen. You can make the thing convenient to yourself, you know. In civil matters you do not actually have to testify in court. You can give a deposition at a lawyers office or a court reporters office at your convenience and the lawyers can read the deposition in court. But whether a lawyer wants to call you to testify in court or to read your deposition in court is usually up to the lawyer unless you are sick, missing or dead at the time of the trial.
But if you do not get a subpoena, then you have no obligation to volunteer your testimony. Furthermore, you are entitled to a statutory witness fee and mileage attached to the subpoena which has to be served on you by a process server. And if you are an expert witness, you are entitled to big bucks depending on what you are an expert on.
The foregoing is offered for informational purposes only and is not legal advice nor does it create any kind of attorney-client relationship. But if you found the answer helpful, kindly check the thumbs-up box below.
If a subpoena is issued to you ordering that you appear in court, you must do so. Failing to do so could result in your being found in contempt.
THESE COMMENTS ARE NOT LEGAL ADVICE. They are provided for informational purposes only. Actual legal advice can only be provided after consultation by an attorney licensed in your jurisdiction. Answering this question does not create an attorney-client relationship or otherwise require further consultation.