What an Expert Report Must Contain
Rules about report contents look like formalities and are not. Each required element exists because reports that omitted it turned out to be impossible to test, and a missing element is the first thing an opponent will look for and the easiest one to make something of.
The rule in short
A usable expert report identifies the question it answers, lists the material examined, separates assumptions from findings, describes the method, shows the reasoning, states the qualifications relied on and carries the declarations the forum requires. Omissions are treated as weaknesses rather than as tidiness problems.
Report requirements read like administrative housekeeping until a report is challenged, at which point every omission becomes an argument. The elements are not there for tidiness. Each one exists because reports lacking it proved impossible to test.
The core elements
The question. Stated explicitly, in the terms in which it was asked, so that a reader can see whether the analysis that follows actually addresses it or something adjacent to it.
The material considered. Listed item by item rather than described in the aggregate, because a reader needs to know both what was examined and what was not.
The assumptions. Facts taken as given rather than found, identified separately, since an opinion resting on an assumption fails with it and a reader must be able to see the dependency.
The method. What was done to the material, described in enough detail that another practitioner in the field could follow it and understand why it was chosen.
The reasoning. The visible route from material to conclusion, which is the part that allows a decision-maker to adopt some of the analysis and differ on the rest.
The conclusion. Expressed at the level of confidence the material actually supports, with ranges where a single figure would be false precision, and with limits stated.
Qualifications and instructions
Qualifications relevant to this question. Not a full career history but the parts that bear on the specific issue, which is the framing discussed in who qualifies as an expert.
A statement of instructions. What the writer was asked to do, by whom, and on what basis, which is required in several forums and disclosable in more.
Which means instructions get drafted carefully. A letter of instruction steering toward a conclusion becomes an exhibit, and it damages the report far more effectively than any cross-examination.
Material supplied by the instructing party. Distinguished from material the writer obtained independently, because the difference bears on how far the analysis was shaped by somebody else's selection.
Any work done by others. Testing, sampling or analysis carried out by colleagues, identified as such, since an opinion resting on unattributed work by unnamed people is fragile and invites questions nobody present can answer.
Where the material came from. Records obtained from a third party carry their own provenance question, and the routes available are set out in what a records request can and cannot reach.
| Element | Why it exists | Cost of omitting it |
|---|---|---|
| Question stated | Shows the analysis fits | Argument about relevance |
| Material listed | Shows what was seen | Question about what was not |
| Assumptions marked | Shows dependencies | Hidden point of failure |
| Method described | Allows testing | Opinion cannot be examined |
| Declarations | Records independence | Report may be refused |
Declarations and the duty they record
A duty to the forum, not the payer. Most systems require an expert to state that their overriding obligation runs to the decision-maker, and the statement is not a formality.
Disclosure of interests. Financial or professional relationships with a party, prior instructions by the same firm, and anything else a reader would want to know about independence.
A statement of truth or its equivalent. Confirming that the opinion is genuinely held and that the writer has not omitted anything material, with consequences attached to a false one.
Confirmation of expertise. That the writer considers themselves competent in the area addressed, which sounds circular and is in practice a useful restraint.
Where the rules differ. Requirements vary by forum, and a report drafted for one proceeding may lack declarations another requires, which is a common and entirely avoidable problem.
A report written for two forums. Where the same analysis will be used in more than one place, drafting to the stricter set of requirements avoids a second version that differs from the first.
Instructing parties routinely write letters of instruction as advocacy and then discover that the letter is disclosable and forms part of the report. A letter that sets out the question neutrally costs nothing; one that suggests the desired answer is worth more to an opponent than any other single document.
Presentation that survives reading
Numbered paragraphs. So that the report can be cross-referenced in argument, in cross-examination and in any second opinion responding to it.
Appendices for the underlying material. Working, data and source documents attached rather than described, so that the analysis can be checked rather than taken on trust.
A summary that matches the body. Executive summaries drafted more firmly than the analysis supports are the commonest self-inflicted wound in expert reporting.
Plain language wherever possible. Technical vocabulary that is necessary should be defined; technical vocabulary that is not necessary makes the report harder to rely on.
Consistent figures. Numbers that differ between the summary, the body and the appendices are read as carelessness and undermine everything else in the document.
Exhibits identified as they are used. Cross-referencing each conclusion to the specific document behind it lets a reader verify a step without hunting through an appendix bundle for it.
What omissions cost
A missing material list invites the question. What else was there, and an opponent will ask it in a form that suggests the answer is unhelpful.
Unstated assumptions are a hidden dependency. Their discovery is worse than their disclosure would have been, because it suggests they were concealed rather than merely overlooked.
No method means no test. A conclusion without a described route can only be accepted or rejected whole, which is dealt with in an opinion and a conclusion.
Missing declarations may be fatal. In forums that require them, a report without the prescribed statements may simply be refused, whatever its quality.
Late supplementation looks worse. Filling a gap after it is pointed out draws attention to it, and the corrected report carries the correction with it thereafter.
Report requirements are the accumulated record of what went wrong in earlier reports. Each element on the list exists because its absence made an opinion impossible to test, and the rules were written afterwards.
The elements most often neglected are the material list and the assumptions, which are also the two an opponent examines first. Both are easy to include and expensive to have left out.
Instructions deserve particular attention because parties forget that they will be read by somebody else. A neutral letter setting out the question is worth drafting properly, since the alternative becomes an exhibit.
Presentation matters more than it should. Numbered paragraphs, attached working and consistent figures make a report usable, and their absence makes a sound analysis harder to rely on than it needs to be.
For anybody commissioning a report, the practical step is to check the forum's requirements before the work starts rather than after the draft arrives. Retrofitting declarations and material lists is possible and always looks like retrofitting.
Points to carry away
- The question answered should be stated in the report, not assumed.
- Material examined is listed rather than summarized.
- Instructions are frequently disclosable and should be written accordingly.
- Declarations about duty and independence are required in many forums.
- A missing element is an opponent's easiest point.
Questions readers ask
Why does the material list matter so much?
Because it defines the boundary of the analysis. A reader who knows exactly what was examined can assess whether the conclusion follows from it, and can also see what was not examined. A report that describes its material in general terms leaves both questions open, and an opponent will fill the gap with the suggestion that inconvenient material was available and passed over. Listing item by item is more work and removes the argument entirely.
Are letters of instruction really disclosable?
In many forums yes, and in others they become disclosable if the report refers to them or if the writer is asked about them under examination. The practical consequence is that a letter of instruction should be drafted as a document that an opponent will read. A neutral statement of the question, the material supplied and any facts the writer is asked to assume costs nothing to write and gives away nothing; a letter that indicates the answer the instructing party wants is worth a great deal to the other side.
What happens if a report omits a required declaration?
It depends on the forum. Some treat the declarations as mandatory and will not receive a report without them, whatever the quality of the analysis. Others admit the report and treat the omission as a matter going to weight, particularly where independence is in issue. Either way the fix is to check the requirements of the specific forum before the report is drafted, because supplying a missing declaration afterwards draws attention to the fact that it was missing.
Sources
- Federal Rules of Civil Procedure — Rule 26, Duty to Discloselaw.cornell.edu
- Federal Rules of Evidence — Rule 702, Testimony by Expert Witnesseslaw.cornell.edu
- Federal Rules of Evidence — Rule 703, Bases of an Expert's Opinion Testimonylaw.cornell.edu
- Federal Rules of Evidence — Rule 705, Disclosing the Facts Underlying an Expert's Opinionlaw.cornell.edu
- Legal Information Institute — Expert Witnesslaw.cornell.edu
- Federal Rules of Civil Procedure — Rule 35, Physical and Mental Examinationslaw.cornell.edu
True Justice Record is a publication, not a law firm. This article states general rules and cites its sources; it is not advice about any particular case, and the law differs by state and changes over time.
More in Opinion That Counts as Evidence
Who Qualifies as an Expert
A witness may be qualified by knowledge, skill, experience, training or education, and any one of them suffices. The enquiry is whether this person knows something useful about this question, not whether they hold a particular qualification. A separate and prior question is whether the claimed field is one in which expertise genuinely exists.
Paying for an Opinion, and What It Buys
An expert is paid for time and analysis, and that arrangement is normal and disclosed. Fee structures tied to the outcome are treated differently and are prohibited in some fields. The questions that carry weight concern contingency, the proportion of a witness's work from one source, and the extent of instructing-party involvement in drafting.
When an Opinion Is Excluded
Expert evidence is subject to a gatekeeping decision before it is heard. The questions are whether the subject genuinely admits of expertise, whether the witness possesses it, whether the method is reliable and whether the opinion assists rather than usurping the decision-maker. Challenges have to be brought early to be decided properly.