Expert Witness Testimony: What Makes a Medical Opinion Defensible?

By Dr. Steven B. Ross, DC, FASBE, DAAPM

Chiropractic Physician | Fellow, American Academy of Applied Spinal Biomechanical Engineering | Diplomate, American Academy of Pain Management.

A medical expert's role is not simply to reach a conclusion. The opinion must be supported by evidence, explained clearly, and able to withstand scrutiny.

For attorneys, understanding what makes an expert opinion defensible can be especially important when preparing for deposition or trial.

What Makes Expert Witness Testimony Defensible?

A strong opinion should be grounded in the available medical and scientific evidence.

That means the expert should be able to explain:

• What evidence supports the opinion

• How the evidence relates to the reported injury

• Why the proposed mechanism is medically plausible

• Whether alternative explanations were considered

• What limitations exist within the available evidence

The goal is not to make an opinion sound more certain than the evidence allows. It is to clearly explain what the evidence supports and where its limitations lie.

The Difference Between a Conclusion and an Explanation

Simply stating that an accident caused an injury does not explain why.

A defensible medical opinion should connect the relevant evidence to the conclusion.

For example, when evaluating injury causation, an expert may need to consider the mechanism of the incident, medical history, clinical findings, diagnostic information, and timing of symptoms.

Each piece of information contributes to the overall analysis.

The strength of the opinion comes from how those pieces of evidence are evaluated together.

Alternative Explanations Matter

A medical opinion becomes more useful when reasonable alternative explanations have been considered.

This does not necessarily mean that every possible explanation must be addressed. Rather, the expert should be able to explain why relevant alternative causes do or do not fit the available evidence.

This is particularly important when a patient has pre-existing conditions, previous symptoms, or other potential sources for the reported condition.

Clear Communication Is Essential

Even a well-supported opinion can become difficult to evaluate if it is not communicated clearly.

Attorneys should be able to understand:

• The evidence the expert relied upon

• The reasoning connecting the evidence to the opinion

• The assumptions involved

• The limitations of the analysis

An expert should be able to explain complex medical and biomechanical concepts in a way that is understandable without oversimplifying the underlying science.

Questions Attorneys Can Ask

When evaluating an expert opinion, consider asking:

1. What evidence supports the opinion?

2. What evidence could challenge it?

3. Were alternative explanations considered?

4. What limitations exist?

5. Can the reasoning be clearly explained under scrutiny?

These questions can help attorneys better understand not only what an expert believes, but why the expert reached that conclusion.

Conclusion

A defensible expert opinion is not necessarily the opinion stated with the greatest certainty.

It is the opinion that can be clearly connected to the evidence, explained through sound reasoning, and appropriately qualified where limitations exist.

For attorneys, understanding that distinction can be valuable when selecting an expert, evaluating an opinion, or preparing for testimony.

The strength of an expert opinion is ultimately measured not only by its conclusion, but by the reasoning and evidence supporting it.

About the Author

Dr. Steven B. Ross, DC, FASBE, DAAPM is a chiropractic physician, spinal biomechanical injury analyst, Independent Medical Examiner, and expert witness with more than 40 years of clinical experience. His practice focuses on injury causation analysis, spinal biomechanics, chiropractic and medical malpractice, independent medical examinations, and evidence-based medical-legal consulting.