Getting It Right – tips for letters of instruction to experts

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A compelling report prepared by an expert witness can be a useful tool in litigation, both in pre-trial settlement negotiations and also in court. One of the most important aspects of creating a good expert report is having a suitable letter of instruction prepared by the instructing lawyer.

So how do you create an effective letter of instruction and what are the issues to be avoided?

Prior to drafting

Before the letter of instruction is drafted, it is useful to confer with the expert about the issues involved in the matter and upon which they are required to comment. The expert may even be able to advise on the type of questions that will help pinpoint the information the lawyers require and, depending upon what stage the litigation process is at, suggest avenues for further discovery.

At this stage, an expert can also indicate areas that are outside their field of expertise. For example, while a physiotherapist may be able to comment on the kind of assistance and/or equipment an injured person may need around their home, they may not be able to comment on the cost of such assistance.

Drafting the letter

An expert’s overriding duty is to the court, not to the lawyer briefing them or the client being represented. For that reason, lawyers need to be cautious that the letter of instruction does not reflect any bias towards simply obtaining an advantageous opinion.


The letter should include a background to the matter and the nature of the dispute. The party names should be clearly identified in the letter, including stating which party/parties the lawyers are acting for.

The admissibility and/or weight of expert opinion evidence will depend on the lawyers being able to prove any assumptions given to the expert and upon which they are asked to rely when preparing their report. For that reason, such assumptions must be carefully drafted as the expert is required to state all assumptions they have relied upon in their report.

It may also be the case that not every assumption can be proven before an expert commences their report.


The letter should also include a list of any documents sent to the expert. It is useful to include the title, date, and document ID (if any). The decision about which documents on which to brief an expert obviously depends on the matter, but lawyers should consider the amount of reading that will be required (and charged for) and send only the documents relevant for the expert to form their opinion. If the expert finds they require further information, they can request it.

Lawyers can create problems for themselves if they do not brief all relevant documents in an attempt to influence an expert’s opinion in a certain direction.


One of the most common issues encountered by experts involves poorly drafted questions. Questions to the expert are the foundation of the report and go to the core of the opinion sought by the lawyers. If they are not drafted carefully, they can result in a report that is vague, unwieldy, irrelevant, and ultimately not useful to the lawyer’s case.

Unhelpful questions include those that:

are loaded or biased (leading questions):

In your expert opinion, when the defendant drove his car into our client’s car, was he excessively inebriated or just moderately inebriated?

‘What makes the software package offered by our client superior to that offered by the defendant?’

narrow the issues in order to produce the opinion desired by the lawyers:

Disregarding any evidence relating to natural wear and tear or erosion of the piping, do you agree that it must have originally been incorrectly installed by the defendant?’

Disregarding diet and exercise, how much weight did the plaintiff lose during the weight loss program?

are closed or assume the answer:

Please comment on the ways in which the defendant’s negligent construction of the wall contributed to it collapsing

are repetitive, asking the same question in several ways:

Was the surgical procedure necessary for our client?

‘Should the surgeon have performed the surgical procedure on our client?

‘Was there sufficient cause for the surgeon to perform the surgical procedure?

are so wide in scope so as to be forensically useless:

‘What causes viral outbreaks?

require the expert to offer a legal opinion:

‘In your opinion, did the defendant’s actions in this matter amount to criminal negligence?’

‘In your opinion, do the overhanging branches of the neighbour’s tree constitute trespass?’

In regard to the last point, lawyers should avoid questions such as ‘Was the defendant negligent?’ or ‘Did the plaintiff breach its duty of care?’ as these relate to specific legal concepts that an expert without legal training is not qualified to answer. Their answers to such questions may therefore be disallowed in court or given less weight. More appropriate questions that can produce information equally helpful would be along the lines of whether, in the expert’s opinion, the party’s actions would be considered to be of a reasonable professional standard and/or in line with accepted peer practice.

To ask or not to ask…

One question that can create issues is asking an expert the open-ended question ‘Are there any further comments you want to make?’ or variations of it. Sometimes this can allow an expert to make helpful and relevant comments about the issues that have not been addressed in the other questions. However, it also has the potential to open the door for experts to make comments that may not be helpful to the client.

For example, a lawyer representing a defendant construction company where a workplace accident has happened could seek an expert opinion about safe work practices on a construction site, asking generally what the standards, legislation, and industry practice constitute the ideal safe work environment. However, asking the expert to comment on anything else relevant could also invite them to comment adversely upon the practices of the construction company at the time of the accident, including attributing liability for the accident.

In a worst-case scenario, this can render an expert report unusable. The expert is not at fault because their primary duty is to the court, and they have given their objective view. But if the question had not been asked, those comments might not have found their way into the report.

There are ways to avoid this potential problem. The first, obviously, is not to ask this type of question of an expert. Ideally, discussions have taken place before the drafting of the report, as outlined above. Potentially, the expert has helped identify the relevant questions to ask to get all the relevant information necessary, meaning only those questions directly related to the issues are required in the letter of instruction.

Some lawyers may ask the question but also include instructions in their letters that the expert NOT comment on liability. This means that inviting ‘any further comment’ will restrict the type of comments the expert can make.


The expert should be informed of:

  • the dates of any examinations and/or site visits necessary;
  • the deadline for the report;
  • the date of any settlement negotiations in which the report will be used and/or orders by the Court for filing and service of the report;
  • the date of any conclaves or joint reports; and
  • if known, the trial date and range of dates in which the expert may be called to give evidence.


Poor communication of deadlines can lead to unrealistic time frames, last-minute panics or, in the worst case, reports not being available when needed.


The expert should be instructed to include in their report a summary of their relevant expertise and qualifications to offer their opinion.

Expert Witness Code of Conduct

The letter should include a copy of the relevant Code for the jurisdiction, and the expert should be instructed to acknowledge having read and abided by the Code in their report. The expert should also be instructed to include a declaration that:

  • they have made all enquiries that they consider appropriate;
  • the opinions expressed by them in the report are genuinely held by them;
  • the report contains reference to all matters that they consider significant; and
  • there are no readily ascertainable additional facts that assist in their conclusions.


A properly prepared letter of instruction will help the expert prepare the most effective and useful report. Careful drafting will focus the expert on the specific matters required by the lawyer and by extension assist the Court with clear and thorough information.


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