Civil Litigation Evidence Legal Topics Litigation Strategy Pretrial Matters

Need Another Expert? Here’s How to Augment Your Expert Designation

When you need another expert to support your client’s case or there’s a change in the general substance of a  previously designated expert, you’ll need to move to augment or amend your expert witness declaration.

The requirements for the moving party’s declaration, the court’s findings, and the additional procedure of lodging expert witness information in court are as follows:


The motion to augment or amend must be accompanied by a declaration, stating facts showing:

  • A reasonable and good faith attempt at an informal resolution of each issue presented by the motion; and
  • That the motion to augment or amend was made promptly after deciding to call the expert witness or to offer the different or additional testimony;


  • Copies of the proposed expert witness information on the expert or the testimony required by CCP §2034.260(c) were thereafter served promptly on all other parties; and
  • The moving party wouldn’t in the exercise of reasonable diligence have determined to call that expert witness or have decided to offer the different or additional testimony;


  • Failure to determine to call that expert witness, or to offer that expert’s different or additional testimony, was the result of mistake, inadvertence, surprise, or excusable neglect.


In addition to finding that the showing made in the moving party’s declaration on the above points is sufficient, the court must:

  • Take into account the extent to which the opposing party relied on the moving party’s original list of expert witnesses; and
  • Determine that the opposing party won’t be prejudiced in maintaining an action or defense on the merits if the motion is granted.

Lodging Expert Witness Information in Court

Although not expressly required by CCP §§2034.610–2034.630, it’s better practice to lodge original documents with the court or, if lodging deposition transcripts, certified copies of the transcript. See CCP §2025.480(h).

The moving party should arrange for the following documents to be lodged with the court “when their contents become relevant to an issue” in the action (CCP §2034.290(c)):

  • The demand for exchange of expert witness information; and
  • All expert witness lists and declarations exchanged in response to it.

All materials physically “lodged” with the court must be accompanied by an addressed envelope with sufficient postage for mailing the material. Material lodged electronically must clearly specify the email address to which a notice of deletion may be sent.

Get guidance on all aspects discovering the identify of experts in CEB’s California Expert Witness Guide, chap 10.

Other CEBblog™ posts you may find useful:

© The Regents of the University of California, 2019. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited.

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