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Law 101: Legal Guide for the Forensic Expert

Purpose of a Deposition

The deposition testimony of an expert may serve many useful purposes. In approaching and preparing for the deposition, it is helpful for the expert to have a clear sense of the opposition's objectives. In general, these include:

  • Securing, under oath, background information and evidence that may be used at trial.
  • Confirming the facts and gathering new information. 
  • Allowing the opposing counsel to ascertain:
    • The expert's opinions.
    • The factual basis for those opinions.
    • The expert's qualifications, experience and training in the field of expertise.
    • How effective the expert's testimony may be at trial.
    • What sort of witness the expert will be. 
  • Locking the witness into a position, conclusion or account that may be difficult for the expert to maintain later at the trial or hearing. 
  • Developing what appears to be a lie or an inconsistency in testimony, and then using it in an attempt to impeach the expert later at trial. 
  • Providing an opportunity for deposing counsel to uncover strengths and weaknesses of the opposing party's case. 
  • Demonstrating to the expert's attorney the extent of knowledge and expertise that the opposition possesses.

Several states currently allow discovery depositions in criminal cases, including Iowa, Missouri, New Hampshire, Florida, North Dakota, Vermont, Texas and Arizona (in limited circumstances). In some of these states, depositions are permitted only in felony cases; others either allow depositions in "any criminal case" or in both felony and more serious misdemeanor cases. Depositions in these states supplement other forms of discovery.

The discovery rules in these states are consistent with rules in many other jurisdictions. If anything, these states' discovery rules tend to be less restrictive. Thus, depositions are not a substitute for other means of discovery. Depositions need not be used in every case to obtain adequate discovery because other avenues of discovery may be sufficient. Some of these jurisdictions specifically combine discovery of prior witness statements with the taking of the deposition.1

Due process does not require that a criminal defendant be given the right to take a deposition for discovery purposes. A refusal to permit the taking of a prospective witness's deposition does not violate a criminal defendant's constitutional right to have compulsory process to obtain a witness because a witness who is within the jurisdiction may be subpoenaed to appear at trial. Likewise, an inherent right to take depositions has not been granted by constitutional provisions granting a criminal defendant the right to examine witnesses for and against him on oath or provisions authorizing the state legislature to provide for the taking of depositions in criminal cases.

1See, e.g., Vt. R. Crim. P. 15(d)(1):

  • The state shall make available to the defendant or his counsel for examination and use at the taking of the deposition any relevant written or recorded statement of the witness being deposed which is in the possession or control of the state and to which the defendant would be entitled at trial.

Also see Ariz. R. Crim. P. 15.3(d), stating that where a discovery deposition is allowed,

  • [a]ny statement of the witness being deposed which is in the possession of any party shall be made available for examination and use at the taking of the deposition to any party who would be entitled to it at trial.

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