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Substantial Evidence and Science,
Law and Logic
with downloadable checklist

By Marjory Harris, Esq.

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Substantial or substandard evidence?

Sometimes it seems that "substantial evidence" is like the yeti, sought after but largely unseen. Like a ghost drifting through the hallways of the WCAB, "substantial evidence" scares the unsuspecting attorney when a WCJ announces that the case cannot be submitted or a case is overturned on reconsideration because the medical evidence lacks it. It reminds the attorney of his or her failure to examine all the details and batten down the hatches. Apart from embarrassment, more work looms just when one thought it was nearing the end.

Since the vast majority of litigated cases settle, with only cursory judicial review, we often accept and ignore the boilerplate of causation and apportionment. We do not argue about substantial evidence, either because it does not seem to be a worthwhile expenditure of time, or we do not even know what it is or recognize its absence.

This article examines the elements of substantial evidence and proposes some methods for getting doctors to provide reports or testimony that meet its requirements. We also provide a downloadable checklist for evaluating reports and preparing requests for supplemental reports or deposition questionnaires.

Definition of Substantial Evidence

The Supreme Court defined substantial evidence as evidence "which, if true, has probative force on the issues. It is more than a mere scintilla, and means such relevant evidence as a reasonable mind might accept as adequate to support a conclusion. It must be reasonable in nature, credible, and of solid value."
Braewood Convalescent Hospital v. Workers' Comp. Appeals Bd. (1983) 34 Cal.3d 159, 164.

The components of "substantial evidence" were summarized in the en banc decision in

In this regard, it has been long established that, in order to constitute substantial evidence, a medical opinion must be predicated on reasonable medical probability. (McAllister v. Workmen’s Comp. Appeals Bd. (1968) 69 Cal.2d 408, 413, 416-417, 419 [33 Cal.Comp.Cases 660]; Travelers Ins. Co. v. Industrial Acc. Com. (Odello) (1949) 33 Cal.2d 685, 687-688 [14 Cal.Comp.Cases 54]; Rosas v. Workers’ Comp. Appeals Bd. (1993) 16 Cal. App.4th 1692, 1700-1702, 1705 [58 Cal.Comp.Cases 313].) Also, a medical opinion is not substantial evidence if it is based on facts no longer germane, on inadequate medical histories or examinations, on incorrect legal theories, or on surmise, speculation, conjecture, or guess. (Hegglin v. Workmen’s Comp. Appeals Bd. (1971) 4 Cal.3d 162, 169 [36 Cal.Comp.Cases 93]; Place v. Workmen’s Comp. Appeals Bd. (1970) 3 Cal.3d 372, 378-379 [35 Cal.Comp.Cases 525]; Zemke v. Workmen’s Comp. Appeals Bd., supra, 68 Cal.2d at p. 798.) Further, a medical report is not substantial evidence unless it sets forth the reasoning behind the physician’s opinion, not merely his or her conclusions. (Granado v. Workers’ Comp. Appeals Bd. (1970) 69 Cal. 2d 399, 407 (a mere legal conclusion does not furnish a basis for a finding); Zemke v. Workmen’s Comp. Appeals Bd., supra, 68 Cal.2d at pp. 799, 800-801 (an opinion that fails to disclose its underlying basis and gives a bare legal conclusion does not constitute substantial evidence); see also People v. Bassett (1968) 69 Cal.2d 122, 141, 144 (the chief value of an expert’s testimony rests upon the material from which his or her opinion is fashioned and the reasoning by which he or she progresses from the material to the conclusion, and it does not lie in the mere expression of the conclusion; thus, the opinion of an expert is no better than the reasons upon which it is based).) [Emphasis added]

Escobedo v. Marshalls (2005) 70 Cal. Comp. Cases 604 (Appeals Board en banc opinion), pet. for rev. den. sub nom. Escobedo v. W.C.A.B. (2005) 70 Cal. Comp. Cases 1506 (writ denied).
What does the law require?

Rule 10606 lists what should be in a medical report for it to have evidentiary weight. Labor Code §4628 sets forth requirements for the admissibility of medical-legal reports. Chapter 2.6 of the
AMA Guides discusses what should be included when preparing reports.

So, the first step in our substantial evidence analysis would be to compare the report to 8 CCR 10606, Labor Code §4628, and 2.6 of the Guides.

The first step is checking for technicalities relating to form
Next we look to the summary in Escobedo and address each item:

1. Reasonable Medical Probability: 51% or more. In the leading case McAllister v. WCAB, 69 CA2d 408, 33 CCC 660 (1968), the court held that the courts and the Board “are bound to uphold a claim in which the proof of industrial causation is reasonably probable, although not certain or convincing. We must do so even though the actual causal mechanism is unclear or even unknown.” [McAllister, 33 CCC at 667.] On the other hand, something that is merely possible falls afoul of the prohibition against "surmise, speculation, conjecture, or guess" (Hegglin, see above).

Just because the evaluator says he or she is saying something with "reasonable medical probability" does not make it so. Causation is always open to inspection, to separate "possibility," or speculation from "probability," or causation.

Causation is always open to inspection, to separate "possibility" (speculation) from "probability" (causation).
2. Germane Facts, Adequate Medical Histories or Examinations, Correct Legal Theories: During the passage of time, the patient may get better or worse, or records may be discovered that change the history the doctor relied on, or legal theories may have evolved. All reports you are relying on must be reviewed with this in mind. Some questions to ask the applicant at deposition or trial (or for an offer of proof):

Q. Do you recall seeing Dr. [AME] in January 2009?
A. Yes.
Q. Has there been any improvement in your condition since you saw Dr. [AME]
A. No.
Q. Did you have a chance to review Dr. [AME]’s reports and deposition testimony?
A. Yes, I read all of them.
Q. Was the history you gave the doctor of your symptoms and complaints substantially accurate?
A. Yes.

All reports you are relying on must be reviewed for changes in the facts or the law
3. Reasoning, or the "how" and the "why"
This is often the missing element in the report, making it merely conclusionary and evidence of little weight, rather than being "substantial evidence" worthy of credence.

Send a letter to the evaluator specifically tailored to his or her report and the facts of your case. For example, an AME opined,

"Incorporating all this information, with reasonable medical probability, under Labor Code Section 4663, I believe that fifty (50) percent of the causation of [IW]'s permanent disability and impairment would be due to the nonindustrial condition of the Kienböck's disease. The remaining fifty (50) percent of the causation of the permanent disability and impairment would be due to the industrial injury of [date]."

Applicant's attorney requested a supplemental report and asked,

"In order to constitute substantial evidence, please explain more specifically how the non-industrial and asymtomatic Kienböck's disease would by itself be responsible for half the impairment. Are you comparing [IW] to someone who had the same injury and treatment but did not have Kienböck's? If so, are there actual cases you have treated or read about in scientific literature?" and "What would [IW]'s work restrictions be had he not had Kienböck's at the time of his injury?"

The supplemental report stated:

"Analysis of apportionment prior to Labor Code Section 4663 would be different such that an argument would exist that 100 percent of [IW]'s permanent disability would be due to the industrial injury of [date], as [IW] stated that he had no subjective symptoms and no subjective or objective work restrictions prior to the industrial injury of [date].

[IW]'s work restrictions without the presence of Kienböck's disease would be highly speculative because the Kienböck's disease was, in fact, present at that time of the injury, and the surgical complications arose out of the treatment for this condition."

The fact is, many opinions on causation do not stand up to closer scrutiny and a demand to explain the "how" and the "why." The explanation may be confusing and muddled, making the original conclusionary statement not substantial evidence. It is up to the judge to decide whether the expert medical opinion constitutes substantial evidence.

Many opinions on causation do not stand up to closer scrutiny and a demand to explain the "how" and the "why."
Attacking Causation and Apportionment

The en banc decision in Escobedo tells us what is required to establish apportionment. Like the yeti, there are rare sightings. Too often we see paragraphs such as this:

"With regard to the cervical spine, ninety (90) percent of the causation of the cervical spine disability would be due to the industrial injury and the remaining 10 percent of the causation of the cervical spine disability would be due to the preexisting nonindustrial conditions of the cervical spondylosis and neural foraminal stenosis."

How and why do these common spinal defects cause current permanent disability? What are the scientific underpinnings, if any, to this conclusion? Does the mere presence of pathology equate to disability?

In a previous article we discussed the science and fiction behind Labor Code Section 4663.

In law, "causation" is a complex concept that often overlaps with general doctrines of analytic philosophy. In medicine, "causation" is also complex. Modern medicine is science-based. In science, there is a method for determining causality, with the gold standard being to prove cause and effect in a way that others can reproduce.

"In the context of disability evaluation, where a particular condition might be linked to the workplace; medical definition of causation requires valid scientific proof; legal definition requires either a probability of > 50% or that the event was more likely than not to be causative." (McGraw-Hill Concise Dictionary of Modern Medicine. © 2002)

For the worker's compensation practitioner, it is not practical, nor of great value, to study the voluminous literature in law, medicine, science and philosophy concerning causation. Here we focus on some practical concepts that can be directly applied to the medical reports we receive on a daily basis, where the forensic evaluator has speculated on apportionment and failed to explain the how and the why, as required by Escobedo, or has given an explanation that runs afoul of the concept of causation of permanent disability.
Does the mere presence of pathology equate to disability?
If an analysis of the apportionment language does not show that it complies with the major apportionment decisions, open your browser and start Googling. There is a wealth of information (and misinformation) online. Reputable sources include major medical clinics such as The Mayo Clinic, medical databases, and accepted medical textbooks such as Wheeless' Textbook of Orthopaedics.

Research the risk factors. Is the doctor apportioning to causation of the condition? That is not allowed when apportioning permanent disability.
United Airlines v. WCAB (Milivojevich), 72 CCC 1415 (W/D-2007). If there are risk factors involved in causing a medical condition, a doctor might find industrial causation if it is more probable than not that the work caused or contributed substantially to the condition (McAllister, above). The same reasoning, using risk factors, cannot apply to apportionment, as risk factors by themselves do not prove causation. The risk factors are determined by epidemiological studies, which by definition do not prove causation.

If the doctor's apportionment language cannot find shelter under a legal umbrella, and the medical umbrella is nonexistent or doubtful, then look to concepts of false causation to debunk the apportionment analysis.

If the doctor's apportionment language cannot find shelter under a legal umbrella, and the medical umbrella is nonexistent or doubtful, then look to concepts of false causation to debunk the apportionment analysis.
Science or science fiction?

To separate science from fiction, be aware of what science regards as proof of causation versus correlation.

Clinical medicine is not a science, and evidence-based medicine may be more experience-based than science-based (see Dr. Feinberg's article in this issue, Evidence-Based Medicine). On the other hand, when a doctor is a forensic evaluator, he or she needs to be held accountable to knowing rules of law, science, and logic. It is thus appropriate to query the doctor about the difference between scientific proof and the doctor's experience.

Click here for an extract from a deposition where the AME abandoned the apportionment given in a report when questioned about causation.

For more information on the scientific method, click here. To download the free Reference Manual on Scientific Evidence, Third Edition, click here.

Remember to do some medical research. Use Google to find good questions to ask the evaluator. For example, if the doctor has apportioned to degenerative arthritis, ask how he is able to distinguish it from traumatic arthritis caused by a specific injury or cumulative trauma from past work. You might be able to convert some or all of the non-industrial apportionment to an industrial CT, so even if the case is "Bensonized" it is better than it is better than non-industrial apportionment.

Logic or logical fallacy? BOLO for fallacies that infest medical-legal reports

Be on the lookout for these common logical fallacies:

1. Ipse dixit ("he himself said it"). Something is true because the doctor said it was. Even if cloaked in "medical expertise" assertions, the attorney should question this and demand the doctor prove the assertions. See a segment of a deposition transcript where "ipse dixit" held sway.

2. Cum hoc, post hoc and other fallacies of causation: "Timing is everything," it is said, but it is not per se proof of causation. Two things can happen at or around the same time but be unrelated. Just as we do not assume our client's high blood pressure was caused by his knee injury, we should not assume the forensic evaluator's apportionment to obesity proves causation of permanent disability.

3. Dicto simpliciter (a commonplace saying without qualification, or sweeping generalization): A common one is that degenerative arthritis causes permanent disability. It may take many questions to persuade the evaluator to abandon that fallacy.

4. Circular logic: Arguing in a circle, or circular reasoning. This is when two conclusions are used as premises to support each other, but unless one accepts one of them as true at the outset, there is no reason to accept the conclusions. So, because someone with permanent disability has degenerative arthritis in a damaged joint does not mean that the degenerative arthritis is the cause of the permanent disability. It might be traumatic arthritis due to the work injury, or it might have no effect on function (compare to contralateral joint). If there is no evidence that is distinct from the conclusion, insist that the forensic evaluator provide that (the "how" and the "why").

There are numerous websites devoted to logical fallacies (see sidebar). An attorney can mine them, learning to recognize and question the forensic evaluator's errors of reasoning.


Just as generic comments about apportionment are not substantial evidence, boilerplate letters questioning apportionment will not likely produce substantial evidence. Tailor the letter or deposition questionnaire to the facts of the case. Also keep the letter brief, clear, and non-accusatory. For how to write effective letters, click here. A professional inquiry may encourage the forensic evaluator to reconsider, without a wounded ego getting in the way.

Logical Fallacies

Fallacy Files

Wikipedia’s List of Fallacies


Skeptics’ Guide to Logical Fallacies

Rhetological Fallacies
The Application of "Substantial Evidence" to
Vocational Evidence

We are focusing more and more on rebutting the rating schedule using Almaraz/Guzman and Ogilvie. We need to make sure any vocational evidence follows the principles discussed above concerning medical evidence. For a VR expert checklist provided by WCJ Colleen Casey, see pages 17 through 20 of “Ogilvie.”


The WCJ is to determine if the expert opinions constitute "substantial evidence." But it is up the litigants' attorneys to ensure that the evidence submitted meets the standard.
Marjory Harris, Esq. began practicing law in 1974 as a defense attorney and later became an applicant's attorney and a certified specialist. She continues to represent injured workers in the San Francisco Bay Area and Inland Empire, and mentors attorneys on big cases.

Reach Marjory Harris at (888) 858-9882 or email to