A witness is someone who has firsthand knowledge about a crime or dramatic event through their senses (e.g. seeing, hearing, smelling, touching) and can help certify important considerations to the crime or event. A witness who has seen the event firsthand is known as an eye-witness. Witnesses are often called before a court of law to testify in trials. A subpoena commands a person to appear. In many jurisdictions it is compulsory to comply, to take an oath, and tell the truth, under penalty of perjury. It is used to compel the testimony of witnesses in a trial. Usually it can be issued by a judge or by the lawyer representing the plaintiff or the defendant in a civil trial or by the prosecutor or the defense attorney in a criminal proceeding. Witness testimony is always presumed to be better than circumstantial evidence. Studies have shown that individual, separate witness testimony is often flawed and parts of it can be meaningless. T