If you are a litigator, you know that oftentimes the testimony of an expert witness can make or break a case. Conducting diligent research and you have completed vetting the expert is only half of the equation. If you want to facilitate the best and most effective expert witness testimony, your communication with the expert from the initial engagement letter through the end of trial is critical, according to the Expert Institute.


Below are some best practices when it comes to your expert witness to make sure your case goes smoothly.


  • Agreements: make sure your retainer agreement or engagement letter is comprehensive and thorough, as it will lay the foundation for your relationship with your expert witness. This should include all important terms, separated in easy-to-read provisions, with clearly stated services to be performed as well as the general preparation that is expected and types of materials to be reviewed. The fee provision should have a concise breakdown of the expert’s fees, the method of payment, and how expenses will be compensated.
  • Conflicts and disqualifications: if your expert was previously disqualified from offering an expert opinion in court, you should find out and discuss the context and background of this disqualification immediately. Depending on the details, the expert may not be useful to your case. Other disqualifications may be due to conflicts of interest. In these scenarios, a two-part test is used by the court to decide whether or not an expert witness should be disqualified.
  • Provide all necessary materials: in order for an expert witness to provide a fully formed opinion, he or she must be provided with all necessary file materials for review. There may be particular procedural rules and regulations governing the distribution of the case file; likewise avoid needlessly producing confidential information as this will be discoverable by the opposing party;
  • Beware written communications: federal courts require expert witnesses to provide a written report under Rule 26 of the Federal Rules of Civil Procedure (FRCP). There is a similar rule, Rule 16, in the Federal Rules of Criminal Procedure. If your case is in federal court, or in state court where the jurisdiction adopts similar rules, mostly all written communications are discoverable. This means emails, notes, and drafts. Accordingly, both the attorney and expert witness must be mindful of written communications;
  • Preparation is key: even if the expert witness has extensive experience testifying in court, direct and cross-examinations should not be overlooked. Thoroughly discuss any weaknesses in the expert witness’s opinion in preparation. Also, prepare a general outline for direction examination and flag the major points you want addressed.


Consistent and clear communication between the attorney and an expert witness is critical to increasing the likelihood of success in a criminal or civil lawsuit. The above tips should help you solidify your case and obtain a good result for your client.