Who Owns the Opinion? The Line Between Expert Judgment and Outside Assistance

By Noah Bolmer

An expert’s opinion might draw from decades of research, established methodologies, technical data, and the work of other professionals. While those materials form the foundation of an analysis, the opinion itself depends on the expert’s evaluation. The distinction between using someone else’s work and adopting someone else’s judgment determines whether the final opinion reflects the expert’s own analysis.  

Background 

Expertise is inherently cumulative; no expert develops an entire field of knowledge independent from the work that came before. Scientific research, engineering principles, medical knowledge, and other specialized fields are built through the accumulation and evaluation of information developed by countless people over time. The legal framework governing expert testimony reflects this reality.  

Rule 703 recognizes that experts may rely on information and data that they did not personally generate when those materials are of a type reasonably relied upon by experts in the relevant field. This reflects several common aspects of professional analysis: 

• Experts routinely rely on research, publications, and established knowledge within their field.

Published research, technical literature, professional standards, and established methods provide the foundation for analysis across scientific and technical disciplines. 

• Experts may incorporate data, testing, or analysis performed by others when evaluating a matter.

Many opinions depend on information generated through testing, measurement, observation, or analysis performed by others. The expert’s role is to evaluate the significance of those materials and determine how they affect the opinion being formed. 

• Experts may use specialized tools, methodologies, and resources developed outside their own work.

Technical fields frequently rely on tools and methods created by researchers, organizations, and other professionals. Using established resources allows experts to apply specialized knowledge without independently recreating every underlying process. 

• Experts are expected to apply their own professional judgment when interpreting and relying on those materials.

Reliance on outside information becomes meaningful only when the expert evaluates how that information applies to the specific issue being analyzed. The expert’s judgment connects the underlying materials to the conclusions reached. 

Identifying the Decisions That Define an Opinion 

Some decisions are visible, such as selecting a methodology or determining which facts are relevant to the question being evaluated. Others occur more quietly, such as deciding which assumptions are reasonable, how conflicting information should be weighed, or how much significance a particular piece of evidence should receive. These choices define the direction and substance of the final opinion. 

Those analytical decisions are where an expert’s professional judgment becomes most apparent. Two experts can review the same underlying information and reach different conclusions because they interpret the significance of that information differently. The value of an expert opinion comes from the reasoning applied to the facts and the expert’s ability to explain why those conclusions follow from the analysis. For that reason, experts should be able to identify the points where their own judgment affects the outcome. Those decisions distinguish an opinion grounded in the expert’s own expertise from one that simply adopts conclusions reached elsewhere. Understanding that distinction is essential. 

When Reliance Becomes Something More 

In Dura Automotive Systems of Indiana, Inc. v. CTS Corp., the Seventh Circuit considered whether an expert could rely on technical analysis performed by others when forming an opinion. The case involved allegations that contamination from a landfill had migrated into groundwater. The expert relied in part on groundwater modeling and related technical work performed by others to evaluate the movement of contaminants. The opposing party challenged whether the expert had independently evaluated the analysis underlying those conclusions. 

The Seventh Circuit recognized that reliance on outside expertise is a normal part of technical work. The opinion explained, “it is common in technical fields for an expert to base an opinion in part on what a different expert believes on the basis of expert knowledge not possessed by the first expert.” The ability to consider another specialist’s work does not prevent an expert from reaching an independent conclusion, so long as the expert understands and evaluates the significance of that work. 

The opinion drew the line when outside contributors move beyond providing information or assistance and begin supplying professional judgment that the expert cannot independently evaluate. “Analysis becomes more complicated if the assistants aren’t merely gofers or data gatherers but exercise professional judgment that is beyond the expert’s ken.” The issue was not that other professionals contributed to the analysis, but that critical technical judgments were made by individuals whose specialized work the expert had not independently evaluated. 

Other appellate courts have reached similar conclusions. In TK-7 Corp. v. Estate of Barbouti, the Tenth Circuit excluded a damages expert’s opinion after he adopted sales projections prepared by another individual without demonstrating familiarity with the methods or reasoning underlying those projections. The court concluded that this was not reasonable reliance under Rule 703 because the expert had effectively assumed “the very matter at issue on which he was called to express his opinion.” Together, Dura Automotive and TK-7 illustrate the same principle: experts may rely on work performed by others, but they remain responsible for understanding and independently evaluating the analytical judgments that support their own opinions. 

Protecting Opinion Ownership 

The distinction between using outside assistance and adopting another person’s judgment is not always obvious during the development of an opinion. Experts may work with extensive materials, technical resources, or other professionals without compromising the independence of their analysis. The key is maintaining a clear understanding of where judgment enters the process and how those decisions shape the final conclusion. 

Several questions can help experts evaluate whether an opinion remains their own: 

1. Identify the decisions that shaped the analysis

These may include selecting a methodology, evaluating competing assumptions, interpreting ambiguous information, or determining the significance of particular evidence. Those decisions define the analytical foundation of the opinion. 

2. Understand the role of each contributor

When others assist with an analysis, the expert should understand and catalogue what they contributed and how that contribution affects the opinion. A person who provides data, performs a calculation, or conducts testing may play an important role without controlling the expert’s conclusions. Understanding the boundary between contribution and judgment helps preserve the expert’s role in the analysis. 

3. Be able to explain the reasoning behind the conclusion

An expert’s opinion should reflect more than familiarity with the materials reviewed. The expert should be able to explain why certain information was relied upon, how competing possibilities were evaluated, and how the analysis led to the final conclusion. The ability to articulate that reasoning demonstrates ownership of the opinion. 

4. Distinguish inputs from conclusions

Experts should distinguish between materials that inform an opinion and conclusions that have already been reached by someone else. A contributor may provide data, calculations, or analysis, but the expert should understand whether that work represents an input to the opinion or a judgment that directly affects the conclusion. Making that distinction helps preserve the connection between the expert’s reasoning and the final opinion. 

Conclusion 

An expert’s role is defined by the decisions that shape an opinion. Understanding which judgments affect the analysis, how those judgments were reached, and how they connect to the final conclusion allows an expert to explain the foundation of the work with clarity. Outside contributions may form part of that process, but the expert must retain ownership of the judgments that shape the opinion. 

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