Working with experts
Written on the assumption that an opponent will read it closely
An expert report is not a summary of a conclusion. It is the reasoning, the data and the assumptions, set out so that someone determined to break it can try.
Qualities
What makes a report durable
Traceable reasoning
Every figure can be followed to its source. An adjustment with no stated basis is an invitation.
Complete materials list
Everything considered, including what did not support the conclusion. Omissions found later do more damage than the material would have.
Explicit assumptions
Each one identified, with its source. Assumptions supplied by counsel are defensible; assumptions adopted silently are not.
Stated limits
What the opinion does not cover. An expert who claims more than their analysis supports loses the parts that were sound.
Internal consistency
No conclusion that contradicts an assumption elsewhere. This is the first thing a competent reviewer looks for.
Legible to a non specialist
The fact finder is not an appraiser or an engineer. A report only another specialist can follow will not persuade anyone.
What surrounds it
The file is part of the evidence
In most jurisdictions a testifying expert’s working file is discoverable: data, calculations, photographs, correspondence and often drafts. Rules on drafts and on communications with counsel vary significantly, and in federal practice some protections exist that many state courts do not mirror.
The practical consequence is that the file should be built as though it will be produced, because it probably will be. That means organised data, recorded verification of comparable sales, dated photographs and no commentary in the file that the expert would not want read aloud.
Settle the draft question at retention. Whether drafts are retained, and what protection applies to them in this jurisdiction, should be decided before the first one exists rather than after.
Weaknesses
What opposing counsel looks for first
| Weakness | How it gets used |
|---|---|
| A conclusion with no supporting analysis | Established in two questions, then characterised as assumption |
| Materials omitted from the list | Produces the suggestion that unfavourable evidence was set aside |
| An assumption outside the expert’s field | Grounds for exclusion of part of the opinion, and damaging to the rest |
| Inconsistency between sections | Undermines the whole report regardless of which part was right |
| A method departing from standard practice | Opens an admissibility challenge |
| Prior testimony taking the opposite position | Produced and read back, and it is always found |
Questions about the report
Can counsel comment on a draft
Practice varies and some involvement is normal. What is not acceptable is counsel shaping the opinion. Assume the extent of involvement will be explored in deposition.
Should the report include unfavourable facts
Yes. A report that addresses the weakness and explains why it does not change the conclusion is far stronger than one that omits it and is confronted with it later.
How long should it be
As long as the analysis requires. Length is not credibility; traceable reasoning is. Many strong condemnation reports are shorter than the weak ones they oppose.
What if the expert changes their opinion
It should be documented and disclosed. An opinion that shifts without explanation is the most damaging thing in any expert’s file.
The expert decides the number more often than the argument does
In condemnation the facts in dispute are technical. Who presents them, and how well, is usually what the case turns on.