Most jurisdictions provide that depositions may be taken to perpetuate the testimony of a witness, that is, preserve their testimony for trial. If the person requested to testify (deponent) is a party to the lawsuit or someone who works for an involved party, notice of time and place of the examination before trial can be given to the other side's attorney, but if the witness is an independent third party, a subpoena must be served on him/her if he/she is recalcitrant. This occurs when a witness may not be able to testify at trial. The deposition of the witness is taken and, if the witness is unable to appear at trial, the deposition may be used to establish the witness' testimony in lieu of the witness actually testifying. Regarding depositions to preserve testimony, the Confrontation Clause of the Sixth Amendment to the United States Constitution establishes a constitutional right of the defendant to be present during the deposition and to cross-examine the witness. The defendant may waive this right.