The criminal justice system cannot function effectively without the full cooperation of witnesses. If you have particular knowledge about the commission of a crime, it is likely that you will be called upon to serve as a witness at the criminal trial.

Witnesses are not necessarily "eye witnesses." You may not have actually seen or heard the crime happen, but you may know something about it. Or, you may have information about a piece of evidence, or knowledge that contradicts the testimony of another witness.

The Subpoena

Usually, when the trial date has been set, you will be notified by a subpoena, which you should not ignore. You may face serious penalties for failing to appear in court as directed at the relevant date and time. If, for any reason, you are unable to appear as the subpoena directs, you should immediately notify the prosecutor handling the case whose name and contact details will appear on the document.

The Oath

When you are called to the stand to testify, you will be asked by the court clerk to confirm that you intend to tell the truth. Your answer will be “I do,” and you should ensure that you abide by this promise. Prepare to answer the attorney's questions to the best of your memory and do not try to work out whether your answers will help or hurt either party. The defendant will be present in court to hear what all the witnesses say about him or her, but this should not affect the truthfulness of your testimony.

Giving Testimony

The Assistant United States Attorney (AUSA), who represents the prosecution, will ask you questions for the purpose of “direct examination.” The objective of direct examination is for you to tell the court what you know about the case.

Questioning by the defense attorney is called "cross-examination." Cross-examination questions will challenge your version of events and are meant to raise doubts about the accuracy of your testimony. Try to remain calm and courteous during cross-examination, as the defense attorney is just doing their job. The judge and the jury will be paying attention to whatever you say as well as to your demeanor. Although you are responding to the questions of a lawyer, remember that the questions are really for the jury’s benefit.

Answer Only What You Are Asked

You should answer only the questions asked of you. You should not volunteer any information that is not actually asked for, even if you feel tempted to do so. Do not give your opinions on any matter, as opinions are not facts. Do not state what someone else told you, unless the relevant attorney specifically asks you to do so.

It is possible that you might give an inconsistent testimony by saying something earlier in the questioning that does not support something you mention later on. If you make such a mistake during your testimony, try not to get flustered; you should just explain clearly why you made the prior error. After all, the jury is comprised of human beings, who can acknowledge that people make honest mistakes.

Objections by Attorneys

If the defense attorney’s cross-examination is improper, the AUSA will raise an objection. You should not attempt to answer a question that the AUSA has objected to. The judge will either “allow” the objection or “overrule” it. Wait for the judge to tell you to continue before answering any further questions. If a question is asked and the AUSA does not object, you will have to answer it—even if you would rather not.

Do Not Discuss Your Testimony

After you have testified in court, you should not tell other witnesses what was said or asked during the testimony until after the trial is completely over. You should not ask other witnesses to discuss their testimonies either.

Do Not Discuss the Case

It is possible that jurors who are or will be serving on the case in which you are a witness may be present in the same public areas as yourself. For that reason, you must not discuss the case with anyone. Those jurors may have an opportunity to observe how you act outside of the courtroom and your behavior may affect your credibility.

Talking to Others about the Case

Before you testify, it is perfectly proper for you to have talked with the prosecutor, police or family members. If you are asked whether you have spoken to anyone about the case, you should respond truthfully.

Even though you may have been subpoenaed by the prosecution, witnesses do not belong to either side of a criminal case. Therefore, it is not unusual for the defense to try to talk to you. The defense attorney or investigator acting for the defendant may request an interview with you. It is entirely up to you whether or not to discuss the case with them. Ask for formal identification before you speak to anyone on either side.

Who Can Attend Court with You?

You may bring friends or relatives with you to court, and it may be acceptable for them to sit in court while you testify, unless they too are witnesses. Alternatively, a victim-witness advocate may be present in court with you, if you so require.

What If You Are Threatened because of Your Testimony?

Threatening, harassing or intimidating a witness is a federal crime, whether it is done by the defendant or others connected to him or her, and it is a matter that the courts take very seriously. If you are being threatened or harassed because of your contribution to the case being tried, you should immediately inform the AUSA or, in emergency situations, call the police.

Payment for Your Services

If you were subpoenaed by the federal government, via the AUSA, you are entitled to a witness fee for each day that you are required to appear in court, and a fee per mile round trip from your residence to court. Although you will be absent from work, you will not be reimbursed for lost wages. If you believe that your employer may object to your absence, the AUSA can contact your employer and explain your responsibilities as a witness and the need for your absence from work. Your employer is prohibited from taking disciplinary action against you.

The Outcome of the Trial

A criminal trial may last for days, weeks or even months if there are delays. When all the witnesses have been heard and both sides have rested, the prosecution and the defense have an opportunity to argue the merits of the case to the jury, in what is called a closing argument. The judge or the jury will then make findings and deliver a verdict of guilty or not guilty of the offense charged.