Intended for healthcare professionals


How to be a medical expert witness

BMJ 2015; 350 doi: (Published 09 January 2015) Cite this as: BMJ 2015;350:g7856
  1. Melanie Rowles, head of claims management, Medical Protection Society
  1. melanie.rowles{at}


Melanie Rowles explains the part medical expert witnesses play in clinical negligence cases and other situations and offers advice for those considering taking on the role

Most clinical negligence cases stand or fall on the quality of expert evidence, and so being an expert witness is crucial to the legal process. It is an opportunity to expand your knowledge base, challenge yourself, and add variety to your career. It can also be financially rewarding, offer chances to interact with the legal profession, and provide unique opportunities to reflect on your own clinical practice.

Role of an expert witness

The primary function of professional medical experts is to provide the court with an independent opinion on the clinical issues involved in a case to help the court make a decision on questions falling within that expert’s specialist field. Their role is to assimilate the facts of the case, consider the questions asked of them, and formulate an opinion on the clinical issues based on their experience and qualifications.

If you would like to be an expert witness, you will have to have been successful in your particular field for at least 10 years and to retain a good reputation to be considered to be an “expert.” You must have the relevant skills and knowledge, be up to date on guidance and protocols, and have current and extensive experience in carrying out the procedures on which you may be asked to offer an opinion.

As a medical expert, you may be asked to provide an expert report in a number of settings. In a personal injury claim, you may be called on by the claimant’s solicitors to provide a report on the extent of the injuries and the patient’s prognosis.

In clinical negligence cases, you could be expected to give an opinion on whether a doctor’s actions were of the standard expected of a clinician with similar skills, training, and experience. Failure to reach such a standard would be referred to as a breach of duty. You may be asked to give an opinion on what resulted from the breach of duty, including the length of time the patient may have suffered pain or may expect to suffer in the future or additional procedures that would not have been necessary had the breach not occurred.

You may also be concerned in cases of doctors referred to the General Medical Council (GMC) and be asked to comment on the doctor’s fitness to practise based on the facts of the case and possibly attend an inquest. In cases involving revalidation, you could be asked to look into whether the right courses have been completed by the doctor and whether an effort has been made to achieve the correct level of competency.

Writing the report

When accepting instructions, you must ensure that you are appropriately qualified. For example, if you are reporting on standard of care, the case must concern a doctor working in the same discipline as yourself, otherwise you will not be able to provide a comment on their management of a patient. You should be able to provide an analytical, objective, balanced, and accurate opinion. You should not just give a factual account of the case or be seen to “sit on the fence,” but provide an opinion based on the balance of probabilities (that is, a likelihood of 51% or more).

Expert reports are used by solicitors to assess the likelihood that a claim will be successful, the share of liability that can be attributed to any particular party, and the level of compensation that should be paid.

Before you accept instructions, you should also ensure that you do not have any conflicts of interest, such as knowing or having worked with any of the doctors concerned. Doctors cannot act as independent expert witnesses if they are familiar with the people involved.

The report should be written using terminology and language that can be easily understood by those instructing you, and you should ensure that it could not be misleading. Any conclusions that you come to must be based on evidence in the case, your own specialist knowledge, and published references. You must not deliberately leave out relevant information, and you should take reasonable steps to check the accuracy and completeness of all information before submitting the report.

You may need to see and examine the patient yourself to be able to provide an accurate report. Once you have written a report for the instructing solicitor, you could be asked to attend a meeting with the client, the solicitor and counsel, and in some cases a representative from the defendant doctor’s medical defence organisation.

You may also be required to attend court to provide evidence, but in clinical negligence claims the vast majority are discontinued or settled before they reach court. However, you should be aware that any opinion you provide will be relied on by the person seeking it, and that decisions about how to proceed will be based on your views. You should always assume that you will have to justify the same to a court or tribunal.

Legal duties of an expert witness

Whether you are acting as an expert in civil, GMC, or coroner’s proceedings, you are expected to work within a fairly strict legal framework as laid down in the Civil Procedure Rules. This duty to the court is paramount, and you are required to give independent evidence, uninfluenced by the pressures of litigation and over-riding any duties to the instructing solicitors. You must be familiar with part 35 of the Civil Procedure Rules and the Practice Direction, which provides guidance on the expert’s role and responsibilities, as well as the GMC’s guidance “Acting as an Expert Witness.”

When considering whether to accept instructions to act as an expert witness, you should bear in mind that the instructing solicitor has to comply with strict court deadlines to which you too must adhere. If there is a trial or hearing, you may be asked to attend for several days, and so you should be prepared to make arrangements so that it does not have an impact on your clinical practice.

If you are requested to attend court, you must fulfil your duty and comply with the rules of the courtroom, whereby you may be asked to back up the opinion you gave in the report. Experts might have to pay for wasted costs if they disregard their duties. The judge will determine if an expert witness is guilty of this, and it could be based on whether they have written points that were one sided, not based on evidence, or inconsistent with the records.

If at the outset you think you may be unable to meet all the obligations, you should inform the instructing solicitors so that they can decide whether to instruct another expert.

What makes a good medical expert?

As an expert witness, the GMC requires you to be “honest, trustworthy, objective and impartial.” The GMC’s guidance says, “You must not allow your views about any individual’s age, colour, culture, disability, ethnic or national origin, gender, lifestyle, marital or parental status, race, religion or beliefs, sex, sexual orientation or social or economic status to prejudice the evidence or advice that you give.”

It is important to be professional and to maintain a good attitude, particularly under cross examination. You should remain alert to how upset, confused, or angry the patient’s family are, and treat family members with respect. You will be making important judgments about people’s lives, so it has to be done in an appropriate, sensitive, and tactful way.

Views will be challenged in the trial process, so experts must be able to withstand a certain amount of attack. In the witness box, you could be confronted by new arguments and you will have to respond to the best of your knowledge. If your opinion changes during the course of a case you should tell the solicitor who instructed you before you reach the witness box.

You should restrict your opinion to specific areas in which you have relevant knowledge and direct expertise. A paediatric orthopaedic surgeon should not accept instructions on adult orthopaedic surgery if he or she has not carried out the procedure criticised for many years. Your expertise must be relevant at the time of the criticism and at the time of the report.

Occasionally an opinion is needed on acceptable practice from many years ago. If you have any doubts about whether you are competent to act, speak to your medical defence organisation.

Writing an expert report

What to do
  • Make sure that you fully understand your instructions and the questions you are being asked to answer. If your instructions are unclear, ambiguous, inadequate, or conflicting, seek clarification from the instructing solicitor. If you are unable to obtain sufficiently clear instructions, you should decline to act as an expert.

  • Read all the documentation that is sent to you, especially the medical records.

  • Identify missing material before writing your report, as this may impact on your opinion.

  • Provide a realistic timescale for preparing your report and keep to it. If you need extra time, notify the instructing solicitor immediately.

  • Prepare your report in accordance with the solicitor’s letter of instruction and remember to respond to specific questions in individual paragraphs.

  • Quote accurately from the medical records.

  • Where there is a conflict of factual scenarios, provide your opinion on outcome based on each of the factual scenarios. This shows balance and objectivity.

  • Provide full reasoning for how your opinion is reached.

  • If your opinion is sought on current condition and prognosis, make sure you see the patient and are able to independently identify him or her.

  • Keep your medical defence organisation fully informed about the type of professional work you are doing so that you are appropriately protected.

What not to do
  • Provide an opinion on an issue outside your area of expertise. For example, do not give an opinion on breach of duty when you were instructed only to provide an opinion on causation.

  • Rely on anyone else’s summary of the medical records.

  • Give an opinion on which party’s evidence should be believed. This will lay you open to vigorous cross examination. It is for the court to decide on conflicts of fact.

  • Fail to disclose your involvement in any GMC fitness to practise findings. You should give full disclosure to the instructing solicitor at the outset so that they can assess whether this is likely to impact on your credibility. If it comes to light for the first time under cross examination, your evidence could be severely undermined.

  • Accept instructions where you have a potential conflict of interest—for example, if you have treated the patient or you know the practitioner personally. Discuss any potential conflict with the instructing solicitor and they will advise you whether it prohibits you from acting.


  • Competing interests: I have read and understood BMJ’s policy on declaration of interests and declare no competing interests.

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