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The Importance of an Expert Witness in Complex Litigation cases

Manaswee Wongsuryrat, Nasree Achwarin

Witnesses serve as primary sources of evidence for either proving or refuting the counterparty's claims in legal proceedings. While there are various types of witnesses, an 'Expert Witness' holds particular significance in complex litigation cases due to their specialized knowledge. Complex litigation often involves intricate factual complexities, requiring expertise in specific business areas, where expert witnesses play pivotal roles. The involvement of expert witnesses can significantly impact the outcome of proceedings.

So, what precisely is an 'Expert Witness'? An expert witness is an individual with specialized knowledge, skills, education, or experience in a specific field, summoned to provide expertise during legal proceedings. This aids the court in comprehending complex technical or scientific issues. A proficient expert witness not only possesses professional proficiency, relevant education, and credentials exceeding layperson understanding but can also simplify complex information for both counsels and judges. Examples of expert witnesses include doctors, psychologists, psychiatrists, university professors, engineers, architects, and legal experts.

Under Thai legal system, an Expert Witness is recognized and plays an important role in both Civil and Criminal cases, particularly addressed in Sections 98 and 99 of the Civil Procedure Code, provided below.

Section 98. Either party may call any person to act as his or her witness, who is knowledgeable and specialised, whether by profession or not, in art, science, skill, trade, his or her profession or foreign law and whose opinion in the capacity of a witness may be beneficial in decision-making of the relevant issues.

Section 99. If the court views that it is necessary to inspect a person, object or place or appoint an expert as provided in sections 129 and 130, the court, when it sees fit regardless of the stage of the trial or upon the request of any party under the provisions of sections 87 and 88, shall have the power to issue an order of such inspection or appointment of such expert.

The provision of this section shall not preclude the party from calling a person who is knowledgeable and specialised to act as the party’s witness.”

According to these sections, any party may bring in an expert witness, and the court or the parties may appoint a court-appointed expert.

Similarly, in Criminal case, Expert witnesses are mentioned in Section 243 of the Criminal Procedure Code, detail as follows.

Section 243. Any person who is specialised, by profession or otherwise, in any matter, such as science, art, skill, commerce, medicine or foreign law, and whose opinion may be beneficial in decision-making, inquiry, preliminary examination or trial of the case, may act as a witness for particular activities, such as a physical or mental examination of the injured person, accused or defendant, handwriting examination, experiment or other activities.

An expert may provide his or her opinion in writing, but a copy of such writing must be submitted to the court and to the other party for acknowledgement, and shall appear to give testimony in support of such writing, unless there is necessity or the party does not wish to examine such expert. The court may admit such written opinion in the absence of the expert’s testimony in person.”

In summary, an Expert Witness is recognized as an essential witness type in both Civil and Criminal cases in Thailand, especially in cases involving complex issues such as science, art, skill, commerce, medicine, or foreign law.

Here are key reasons why expert witnesses are important in complex litigation.

  1. Case strategy Expert witnesses play a crucial role in the pre-litigation stage of legal proceedings. By consulting with an expert witness early on, a responsible attorney can assess the merits of a case more accurately. The analysis of facts and evidence by an expert witness allows for a more informed evaluation of the strengths and weaknesses of the case, which, in turn, helps attorneys develop effective litigation strategies, plan evidence collection, and strengthen an attorney's negotiating position.

  2. Clarity In lawsuits related to complex technical details, scientific issues, or industry-specific information, it is generally very difficult to understand from the viewpoint of a person who is not familiar with such fields. The inclusion of an expert witness will assist both legal counsels and judges in better understanding the issue at hand by simplifying complexities and clarifying some acts in the disputed issue. This clarification will be useful in both the pre-litigation stage and the trial stage. 

  3. Corroboration An expert opinion is usually considered academically impartial and can be used as key evidence to support a party's claim in court. By presenting facts and interpretations of technical issues, their testimony and opinion can effectively help support the validity of a party's argument.

Given the invaluable role an expert witness plays in complex litigation cases, it is highly recommended that parties engaged in complicated legal disputes proactively establish an expert witness or consulting plan during the initial phases of the litigation process.



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