ADJ8545914 · August 28, 2026

The Appeals Board found that the medical evidence was insufficient to apportion disability with reasonable medical probability due to intertwined injuries and deferred permanent disability and apportionment for further factual determination.

From the decision · page 1on June 3, 2024. The workers’ compensation administrative law judge (WCJ) found that applicant, while employed by defendant as a Detention Services Officer during the period of October 1, 2009 to January 1, 2012, sustained injury arising out of and in the course of her employment (AOE/COE) to her right wrist, right hand, left knee, heart, lungs, psyche, headaches, and gastrointestinal system, resulting in 100% permanent disability. Defendant contends that the WCJ erred and acted in excess of her powers by failing to apply apportionment correctly pursuant to Labor Code sections 4663 and 4664. 2 Furthermore, defendant 1F

Medical evidence showed intertwined injuries with synergistic effects preventing reasonable apportionment.

Favours Applicant prevailed

This supported deferral of permanent disability and apportionment issues due to speculative apportionment.

From the decision · page 5“This examiner cannot with reasonable medical probability, parcel out the approximate percentages to which each distinctive industrial injury causally contributed to the applicant's overall permanent disability on a psychiatric basis therefor, I will state that I am able to make an apportionment determination and that determination is as follows: Approximate percentage of disability caused by each of the relevant issues in this case cannot reasonably be determined … There is a synergistic effect between the two or more injuries which does not allow permanent disability from one to be separated from the permanent disability from the others (i.e. the overall disability is greater than simply the sum of the injuries, such that each part cannot be reasonably evaluated separately).” (Exhibit X1).

Could not reasonably apportion psychiatric disability due to synergistic effect of multiple injuries; overall disability greater than sum of parts.

Synergistic effect of injuries prevents reasonable apportionment.

From the decision · page 5“This examiner cannot with reasonable medical probability, parcel out the approximate percentages to which each distinctive industrial injury causally contributed to the applicant's overall permanent disability on a psychiatric basis therefor, I will state that I am able to make an apportionment determination and that determination is as follows: Approximate percentage of disability caused by each of the relevant issues in this case cannot reasonably be determined … There is a synergistic effect between the two or more injuries which does not allow permanent disability from one to be separated from the permanent disability from the others (i.e. the overall disability is greater than simply the sum of the injuries, such that each part cannot be reasonably evaluated separately).” (Exhibit X1).

Attributed entire disability to industrial injury and medical treatment complications; apportionment inherently speculative due to overlapping injury periods.

Overlap and intertwining of injury periods make apportionment speculative.

From the decision · page 10On January 26, 2023, he provided deposition testimony addressing the complexities of apportionment. He confirmed he had previously attempted to apportion the disability by assigning one-third to prior specific injuries and two-thirds to cumulative trauma in his August 22, 2022 report. (Court Ex. Z10, p. 6:4-7; Court Ex. Z11, pp. 2-3.) However, he testified that the specific dates of injury and the cumulative trauma periods overlap and intertwine rendering apportionment inherently speculative. (Court Ex. Z10, p. 10:2-9.) He stated that apportioning the disability among the three dates of injury in accordance with Benson to a reasonable degree of medical probability would merely be a gross estimate. (Id. at p. 10:20-25 to 11:1-16.) He concluded that the original injuries leading to the infection are responsible for the overall condition and that determining an exact apportionment percentage remains difficult and highly speculative. (Id. at pp. 11:19-25 to 12:1-10, 13:9-18.) On September 22, 2014, AME Dr. Hyman evaluated applicant in the field of internal medicine. She subjectively complained of experiencing chest pain, palpitations, and ankle swelling

Documented history of industrially related orthopedic injuries; minor residual impairment due to altered lung circulation.

From the decision · page 116.) An electrocardiogram showed a sinus rhythm with right bundle branch block formation, while an echocardiogram by Ram Dandillaya, M.D., dated September 22, 2014 revealed a bioprosthetic tricuspid valve, a pacing catheter in the right-sided chambers, mild tricuspid regurgitation, and an estimated ejection fraction of 60%. (Id. at pp. 7, 18.) AME Dr. Hyman noted that pulmonary function testing demonstrated no significant residual limitation, though he assessed minor residual impairment due to altered lung circulation. (Id. at p. 8.) He opined that applicant sustained a documented history of industrially related orthopedic injuries to her left knee requiring repeated surgical interventions.

Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 621 (Appeals Board en banc)

Apportionment must be established by substantial medical evidence framed in terms of reasonable medical probability and not speculative.

Applied to reject defendant's apportionment claim due to lack of substantial evidence.

From the decision · page 20an adequate examination and history, and it must set forth reasoning in support of its conclusions.” (Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 621 (Appeals Board en banc).) “[T]he medical cause of an ailment is usually a scientific question, requiring a judgment based upon scientific knowledge and inaccessible to the unguided rudimentary capacities of lay arbiters.” (Peter Kiewit Sons v. I.A.C. (McLaughlin) (1965) 234 Cal.App.2d 831, 839 [30 Cal.Comp.Cases 188].) “In a field which forces the experts into hypothesis, unaided lay judgment amounts to nothing more than speculation.” (Id. at p. 840.) The requirement for expert medical evidence exists throughout workers compensation proceedings, including determination of temporary disability, permanent disability, apportionment, and causation of injury to name a few. (See also Escobedo, supra, 70 Cal.Comp.Cases at p. 621 [wherein the Appeals Board required that apportionment under section 4663 be established by substantial medical evidence].) 5 4F

Defendant failed to prove apportionment with substantial medical evidence as required by Labor Code section 4663 and Benson.

From the decision · page 18As stated above, in our prior Opinion and Order Granting Petition for Reconsideration and Decision After Reconsideration, dated January 24, 2024, we rejected defendant’s contention that the WCJ had improperly circumvented the statutory apportionment requirements imposed by section 4663 and Benson. We explained that, because defendant bore the burden of proving apportionment, its failure to carry that burden warranted an unapportioned award of permanent disability, and we further held that we had no duty to require development the record to assist defendant in satisfying that evidentiary burden. Nevertheless, in our subsequent Opinion and Order Granting Petition for Reconsideration, dated August 9, 2024, we found good cause to grant reconsideration and defer a final decision. This deferral allowed for further review of the AME reporting and the potential applicability of apportionment pursuant to section 4664(c), taking into consideration the interrelationship between the previously resolved stipulations for the October 1, 2008 to October 1, 2009 injury and the currently litigated reopened October 1, 2009 to January 1, 2011 injury. We now issue our decision in accordance with that review.