Washington Expert Witness Rules: What Litigators Need to Know

Expert witness testimony plays a pivotal role in Washington civil litigation, particularly in matters involving professional negligence, product liability, and complex commercial disputes. Washington follows a hybrid procedural model that incorporates structured disclosure requirements and a nuanced approach to admissibility. Attorneys must closely adhere to state court rules and local scheduling orders, as failure to properly disclose or qualify an expert can lead to preclusion or limited testimony at trial.

Designation Requirements

Washington does not use a formal “designation” system through court filings. Instead, expert witnesses are identified through discovery disclosures governed by the Washington Superior Court Civil Rules (CR 26). The key mechanism for designation is the discovery process itself, particularly interrogatories and expert witness disclosures required by court scheduling orders.

Under CR 26(b)(5), a party must disclose:

• The identity of any expert expected to testify
• The subject matter of the testimony
• A summary of the facts and opinions the expert is expected to offer
• The grounds for those opinions

Although Washington does not require full expert reports in all cases, detailed summaries are essential. Courts may exclude or limit expert testimony if disclosures are untimely or incomplete under CR 37.

Expert Disclosure Process

Expert exchange in Washington is guided by civil discovery rules and the Case Scheduling Order (CSO) issued by the court. These CSOs typically establish:

• A deadline for disclosure of primary expert witnesses
• A later deadline for rebuttal or responsive experts
• A final cut-off for expert discovery, including depositions

Per CR 26(b)(5)(A)(i), parties are entitled to:

• A list of all opinions the expert will offer
• The basis and reasoning for those opinions
• Supporting materials, including data, literature, and test results
• Compensation information for expert work and testimony

Notably, written reports are not mandatory unless requested through discovery or ordered by the court. However, in medical malpractice and professional liability cases, reports or affidavits may be required to survive dispositive motions.

Required Declarations

Washington does not require expert declarations as part of the initial disclosure process. However, expert declarations are crucial in motion practice, particularly in opposition to summary judgment or in support of motions in limine to admit or exclude testimony.

Under CR 56(e), when a party relies on expert opinion to establish a triable issue of fact, the opinion must be submitted in the form of an affidavit or declaration that:

• Is based on personal knowledge
• Sets forth facts admissible in evidence
• Demonstrates the expert’s competence to testify on the issues presented

In medical malpractice actions, a declaration from a qualified medical expert may be essential to establish a breach of the standard of care and proximate causation.

Fees and Compensation

Expert compensation in Washington is determined by private agreement but must be reasonable. When one party seeks to depose another’s expert, CR 26(b)(5)(C) requires the deposing party to pay:

• A reasonable fee for time spent in deposition
• Compensation for preparation if requested and justified

Fee disputes can be resolved by court motion. Courts generally defer to the expert’s standard billing rate but may adjust fees where they appear excessive or intended to obstruct discovery.

Discovery Scope and Limitations

Washington permits a broad but structured approach to expert discovery. Under CR 26(b)(5):

• The identity, subject matter, and summary of opinions of testifying experts must be disclosed
• Parties may obtain discovery by interrogatories, document requests, and depositions
• Supporting materials and data reviewed or relied upon must be produced

Discovery from non-testifying experts (i.e., consultants retained in anticipation of litigation but not expected to testify) is sharply limited. Such discovery is only permitted upon a showing of exceptional circumstances, consistent with national standards.

Drafts of expert reports and communications between counsel and experts may be protected under the work-product doctrine, although this protection is not absolute and can be waived.

Admissibility Standards

Washington has not formally adopted the Daubert standard, but courts apply similar principles through Evidence Rule (ER) 702 and relevant case law. Under ER 702, expert testimony is admissible if:

1. The expert is qualified by knowledge, skill, experience, training, or education
2. The testimony will assist the trier of fact to understand the evidence or determine a fact in issue
3. The testimony is based on a reliable foundation and valid methodology

In State v. Copeland, 130 Wn.2d 244 (1996), the Washington Supreme Court emphasized that the trial court functions as a gatekeeper, tasked with ensuring the reliability of scientific testimony. Courts may hold pretrial hearings to assess whether the expert’s opinions are based on generally accepted scientific principles and whether they were applied properly.

Washington courts often refer to both Frye and Daubert principles, creating a blended approach where general acceptance remains important for scientific testimony, while reliability and relevance guide admissibility in technical and specialized contexts.

Key Deadlines & Strategy Notes

The Case Scheduling Order (CSO) is the primary document controlling expert deadlines in Washington trial courts. These typically include:

• Initial expert disclosure: Often set 90–120 days before trial
• Rebuttal expert disclosure: 30–60 days after initial disclosures
• Expert discovery cut-off: 30 days before trial or as otherwise ordered
• Motions in limine to exclude experts: Due per the court’s trial management schedule

Strategically, early expert retention is recommended, particularly in cases involving complex science or medical issues. The blended admissibility standard in Washington encourages early vetting of methods, data, and underlying assumptions to withstand scrutiny under either Frye or Daubert reasoning.

State-Specific Statutes & Local Rules

• CR 26(b)(5): Governs expert discovery, including scope and compensation
• CR 37: Provides for sanctions and preclusion for failure to disclose experts
• CR 56(e): Requires affidavits or declarations to oppose summary judgment
• ER 702: Admissibility of expert testimony
• State v. Copeland, 130 Wn.2d 244 (1996): Leading case on admissibility of scientific expert evidence

Local court rules—particularly in King, Pierce, Snohomish, and Spokane counties—may impose unique disclosure requirements or case-specific scheduling practices. Attorneys should consult local rules and individual CSOs for jurisdictional nuances.