Roberts: An Unproven Prior Award and Unexplained AME Percentages

In Roberts v. City of Los Angeles, Nos. ADJ16790298 and ADJ16790299 (WCAB Jan. 9, 2026), the WCAB denied the defendant’s petition for reconsideration after finding that the agreed medical evaluator’s apportionment opinion lacked substantial medical support. The record combined an uncertain reference to a prior award, an eight-percent whole-person-impairment figure and unexplained percentage allocations. Those components did not become reliable simply because the parties used an AME.

This is a fact-specific panel decision, not binding en banc precedent. The panel adopted the workers’ compensation judge’s report and added its own explanation of the substantial-evidence requirement. Its denial left the challenged findings and awards in place; it did not announce a new automatic rule against apportionment involving degeneration or prior injuries.

Two industrial injuries remained distinct

The worker was a firefighter/captain. One claim concerned cumulative trauma from February 10, 2003 through August 25, 2022, involving his back and right carpal tunnel. The other concerned a June 18, 2022 specific injury to the cervical and lumbar spine. The WCJ found permanent disability of 38 percent in the first claim and 42 percent in the second. See page 1.

The defendant challenged the finding that it failed to establish nonindustrial apportionment for the cervical and lumbar disability. The dispute was not whether those accepted industrial injuries existed. Nor should the two stated ratings be added together and presented as a new combined award. Separate claims, impairment measures and causation allocations require their own analysis.

A reference to eight-percent WPI did not prove a prior award

The incorporated report describes the AME’s initial uncertainty about whether the worker had received a prior low-back award. A later report referred to eight-percent whole-person impairment, recommended subtraction and then proposed allocating the remainder approximately 80 percent to the cumulative trauma and 20 percent to the specific injury. See pages 7–9.

Whole-person impairment is not itself proof that a prior permanent-disability award exists. The report identified the absence of evidence establishing the asserted prior award and the confusing relationship between the proposed subtraction and the two industrial claims. A physician’s conditional reference cannot silently supply the missing award document or explain every step of that calculation.

That distinction separates a claimed prior-award credit under section 4664 from causation-based apportionment under section 4663. Failure to prove a prior award does not, by itself, eliminate every possible section 4663 argument. But another contributing factor still requires substantial medical reasoning; calling a number a subtraction does not establish its legal or factual basis.

The percentages needed an explained causal basis

The AME attributed approximately 20 percent of cervical disability to degenerative changes and 80 percent to the June 18 injury. The incorporated report found the nonindustrial attribution inadequately explained. It was not enough to name degeneration without showing why and how the identified factor contributed to the permanent disability on this record. See pages 7–9.

The panel’s discussion at pages 3–5 applies Labor Code section 4663 and the substantial-medical-evidence standard. It requires reasonable medical probability, pertinent facts, adequate examination and history, and reasoning supporting the conclusions. The panel expressly explains that addressing apportionment and giving approximate percentages does not necessarily make the opinion one the WCAB may rely upon.

This does not mean that degenerative pathology can never support apportionment. The defect was the adequacy of the explanation offered, not the existence of a universal exclusion for that category of evidence. Likewise, splitting responsibility between two industrial injuries is different from attributing disability to a nonindustrial cause; one allocation does not explain the other.

The worker’s disability burden did not become the employer’s apportionment proof

The incorporated report distinguishes the worker’s burden to establish the extent of permanent disability from the defendant’s burden to prove apportionment. See page 8. An unsupported employer allocation is not cured by asking the worker to disprove an unestablished premise. Conversely, rejecting a particular apportionment opinion does not dispense with proof of the underlying disability.

The AME’s role did not remove the need to examine the actual report. The opinion must disclose its facts and reasoning; an agreement to use that evaluator does not make every conclusion substantial evidence. The case therefore supports evaluating the causal explanation rather than accepting or rejecting the report solely because of the evaluator’s title.

The result was denial, not a new percentage calculation

The January 9 order denied the defendant’s petition. See page 6. The useful review separates the actual prior award, if any; the impairment measure; the allocation between industrial claims; and any reasoned nonindustrial contribution. Those are different propositions requiring different evidence, not interchangeable labels for reducing a rating.

Our apportionment authority analysis explains the foundational medical-evidence standard. For a review of the specific award documents and AME reports, see our California workers’ compensation practice.