Leading citation
Benson v. WCAB (2009) 170 Cal.App.4th 1535
What this holding is
Benson v. Workers’ Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535 holds that each compensable injury gets its own permanent disability rating unless the physician cannot parcel them. It is not Wilkinson stacking. These are later panels applying that split, not a prediction of any one claim.
How later panels applied it
Newest released decisions whose legal-standard extraction named this holding. Each quotes the passage and links to the official PDF. The leading case is cited the way courts cite it; our own cards stay ADJ, date, and issue. Litigated tail — not a win rate.
- ADJ8973029 · 2026-05-26 · Oakland District OfficeBenson
Determinative passage · p.16A physician must determine apportionment based on causation, because an employer is liable solely for the portion of permanent disability directly attributable to an injury arising out of and occurring in the course of employment. (Lab.Code, § 4663(a) and 4664(a).) "The plain reading of `causation' in this context is causation of the permanent disability." (Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 611 (Appeals Board en banc) (Escobedo).) Apportionment now includes pathology, asymptomatic prior conditions, and retroactive prophylactic work preclusions, provided there is substantial evidence establishing that these other factors have caused permanent disability. Pursuant to Escobedo, a physician's opinion must constitute reasonable medical probability, must not be speculative, rely on pertinent facts and/or an adequate examination and history, and must set forth the reasoning in support of the conclusions. (Id. at p.621.) That is, a physician must explain the "howand why" of their apportionment opinion and consider all potential causes of disability, whether from a current, prior or subsequent industrial or nonindustrial injury or condition. (Ibid.; Benson v. Permanente Med. Group (2007) 72Cal.Comp.Cases 1620, 1622 (Appeals Board en banc).)
Applied to reject Dr. Sussman's apportionment opinion as speculative and lacking adequate reasoning.
Official decision · page 16 → - ADJ11987597 · 2026-04-28 · Sacramento District OfficeBenson
Determinative passage · p.6A. The burden of proving apportionment of permanent disability falls on the employer because it is the employer that benefits from apportionment. (Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535, 1560 [74 Cal.Comp.Cases 113]; Kopping v. Workers' Comp. Appeals Bd. (2006) 142 Cal.App.4th 1099, 1115 [71 Cal.Comp.Cases 1229]; Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 612 (Appeals Board en banc).) In Escobedo the Appeals Board held: (1) section 4663 requires the reporting physician to make an apportionment determination; (2) apportionment to other factors allows apportionment to causation, including pathology, prior conditions, and retroactive work restrictions; (3) applicant holds the initial burden to prove industrial injury and also has the added burden of establishing the approximate percentage of permanent disability directly related to the industrial injury; (4) defendant has the burden of establishing the approximate permanent disability caused by other factors; and (5) a medical report addressing apportionment may not be relied upon unless it constitutes substantial evidence. (Escobedo, supra, at p. 607.)
The Appeals Board reviewed the AME's apportionment opinions under these standards and found some opinions lacking reasoning but ultimately credited the approximate percentages as substantial evidence.
Official decision · page 6 → - ADJ10988642 · 2026-03-19 · Pomona District OfficeBenson
Determinative passage · p.5compensable cumulative psyche injury was based upon the application of claim and/or issue preclusion, rather than an independent judgement on the merits of the evidence submitted in this claim. (See Report on Applicant's Petition for Reconsideration, at pp. 3§ 5.) Accordingly, we consider whether either form of preclusion properly applies here.
The WCAB applied this legal standard to reject the bar of the cumulative psyche injury claim by claim or issue preclusion.
Official decision · page 5 → - ADJ14680333 · 2026-03-16 · Pomona District OfficeBenson
Determinative passage · p.10The burden of proving apportionment of permanent disability falls on the employer because it is the employer that benefits from apportionment. (Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535, 1560 [74 Cal.Comp.Cases 113]; Kopping v. Workers' Comp. Appeals Bd. (2006) 142 Cal.App.4th 1099, 1115 [71 Cal.Comp.Cases 1229]; Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 612 (Appeals Board en banc).)
Applied to reject apportionment medical opinions as conclusory
Official decision · page 10 → - ADJ16389400 · 2026-03-03 · San Bernardino District OfficeBenson
Determinative passage · p.6With regard to the issue of apportionment, section 4663 provides that "[a]pportionment of permanent disability shall be based on causation." (Lab. Code, § 4663(a).) A doctor who prepares a report addressing the issue of permanent disability due to a claimed industrial injury must address the issue of causation of the permanent disability. (Lab. Code, § 4663(b).) Section 4663 requires that the doctor "make an apportionment determination by finding what approximate percentage of the permanent disability was caused by the direct result of injury arising out of and occurring in the course of employment and what approximate percentage of the permanent disability was caused by other factors both before and subsequent to the industrial injury, including prior industrial injuries." (Lab. Code, § 4663(c).) Pursuant to section 4663(c) and section 5705, defendant has the burden of establishing the approximate percentage of permanent disability caused by factors other than the industrial injury. (Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535, 1560 [74 Cal.Comp.Cases 113]; Kopping v. Workers' Comp. Appeals Bd. (2006) 142 Cal.App.4th 1099, 1115 [71 Cal.Comp.Cases 1229]; Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 607 (Appeals Board en banc).)
The WCAB applied these standards to reject Dr. Graham's apportionment opinions as not substantial evidence and to find no basis for apportionment.
Official decision · page 6 → - ADJ12214919 · 2026-02-20 · Van Nuys District OfficeBenson
Determinative passage · p.132. Apportionment under Benson In our en banc opinion in Benson, we explained that limited situations may exist where a joint and several award of permanent disability may issue across multiple dates of injury. (Benson v. Permanente Med. Group, (2007), 72 Cal. Comp. Cases 1620, 1634 (Appeals Board en banc), (emphasis added); aff'd Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535.) Where some aspects of the industrially caused permanent disability form two or more separate industrial injuries that cannot reasonably be parceled out, then a combined joint and several award of permanent disability must issue even though other aspects of the industrially caused permanent disability from those injuries can be parceled out with reasonable medical probability. (See, e.g. Alea North American Insurance Co. v. Workers' Comp. Appeals Bd. (Herrera) (2018) 84 Cal. Comp. Cases 17 [2018 Cal. Wrk. Comp. LEXIS 123] (writ den.); Flowserve Corp. v. Workers'
The Board applied Benson to affirm a joint and several award of permanent disability across both injury dates.
Official decision · page 13 → - ADJ10908652 · 2025-09-16 · Los Angeles District OfficeBenson
Determinative passage · p.10In our en banc opinion in Benson, we explained that limited situations may exist where a joint and several award of permanent disability may issue across multiple dates of injury. (Benson v. Permanente Med. Group, (2007), 72 Cal. Comp. Cases 1620, 1634 (Appeals Board en banc), (emphasis added); aff'd Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535.) Where some aspects of the industrially caused permanent disability form two or more separate industrial injuries that cannot reasonably be parceled out, then a combined joint and several award of permanent disability must issue even though other aspects of the industrially caused permanent disability from those injuries can be parceled out with reasonable medical probability. (See, e.g. Alea North American Insurance Co. v. Workers' Comp. Appeals Bd. (Herrera) (2018) 84 Cal. Comp. Cases 17 [2018 Cal. Wrk. Comp.
The Board noted the need for substantial evidence to support intertwined disability and that the current record was insufficient.
Official decision · page 10 → - ADJ10305799 · 2025-07-22 · Sacramento District OfficeBenson
Determinative passage · p.9In addition, the burden of proving apportionment of permanent disability rests with the defendant. (Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal.App.4th 1535, 1560 [74 Cal.Comp.Cases 113]; Kopping v. Workers' Comp. Appeals Bd. (2006) 142 Cal.App.4th 1099, 1115 [71 Cal.Comp.Cases 1229]; Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 607 (Appeals Board en banc).)
Applied to apportionment issue to assess sufficiency of medical evidence and burden of proof.
Official decision · page 9 →
All 32 decisions applying it →
Also on this
About Benson
What is Benson in California workers’ compensation?
Benson v. WCAB (2009) 170 Cal.App.4th 1535 holds that successive compensable injuries are rated separately unless the physician cannot parcel them. It is not Wilkinson stacking. This page is later panels applying that split.
How does Benson relate to apportionment?
Benson is about separate injuries and separate ratings. Apportionment (and Escobedo) is industrial versus other causes inside a rating. Different questions; they can appear in the same decision.