Escobedo — how-and-why apportionment

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.

• ADJ11349173 · 2026-06-26 · Riverside District OfficeEscobedo

  Determinative passage · p.7In Escobedo, the Appeals Board outlined the following requirements for substantial evidence on the issue of apportionment:

  Medical opinion must disclose familiarity with apportionment concepts, describe apportionable disability, and set forth basis for opinion with reasoning under correct legal principles.

  Official decision · page 7 →
• ADJ10896001 · 2026-06-18 · Oxnard District OfficeEscobedo

  Determinative passage · p.13Construction v. Workers' Comp. Appeals Bd. (Gatten) (2006) 145 Cal.App.4th 922, 927-928 [71Cal.Comp.Cases 1687].) Instead, apportionment of permanent disability is "based on causation" and the "employer shall only be liable for the percentage of permanent disability directly caused by the 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, supra, 70 Cal.Comp.Cases at p. 611.) 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 rely on reasonable medical probability, cannot be speculative, must rely on pertinent facts and/or an adequate examination and history, and must set forth the reasoning in support of its conclusions. (Id. at p.621.) That is, a physician must explain the "howand why" of their apportionment opinion (Ibid.) and consider all potential causes of disability, whether from a current, prior or subsequent industrial or nonindustrial injury or condition. (Benson v. Permanente Med. Group (2007) 72Cal.Comp.Cases 1620, 1622 (Appeals Board en banc).)

  Apportionment opinions by PQME Dr. Brooks and Dr. Tirmizi were speculative and lacked sufficient medical explanation, thus rejected.

  Official decision · page 13 →
• ADJ11953954 · 2026-06-16 · Riverside District OfficeEscobedo

  Determinative passage · p.5To constitute substantial evidence "... a medical opinion must be framed in terms of reasonable medical probability, it must not be speculative, it must be based on pertinent facts and on an 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).)

  The Board emphasized the need for expert medical evidence to support body system assignment for apportionment under section 4664(c).

  Official decision · page 5 →
• ADJ15295325 · 2026-06-15 · Sacramento District OfficeEscobedo

  Determinative passage · p.6[A] medical report is not substantial evidence unless it sets forth the reasoning behind the physician's opinion, not merely his or her conclusions. [Citations.]

  Dr. Karvelas's apportionment opinion was rejected for lack of substantial medical evidence.

  Official decision · page 6 →
• ADJ15346443 · 2026-06-12 · Riverside District OfficeEscobedo

  Determinative passage · p.12(1970) 1 Cal.3d 627 [35 Cal.Comp.Cases 16].) To constitute substantial evidence, a medical opinion must state its conclusions in terms of reasonable probability, avoid speculation, rely on pertinent facts and an adequate examination and history, and explain the reasoning supporting its conclusions. (Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, 621 (Appeals Board en banc) (Escobedo).) Medical reports do not constitute substantial evidence when they contain known errors or rely on facts that are no longer germane, inadequate medical histories or examinations, or incorrect legal theories. Likewise, a medical opinion cannot support the Board's findings if it rests on surmise,

  Applied to evaluate the sufficiency of medical opinions regarding addition of impairments.

  Official decision · page 12 →
• ADJ19403295 · 2026-06-08 · San Francisco District OfficeEscobedo

  Determinative passage · p.7It is accepted that substantial evidence must support the decisions by the Appeals Board. (Lab. Code, § 5903, 5952(d); Lamb v. Workmen's Comp. Appeals Bd. (1974) 11 Cal.3d 274 [39 Cal.Comp.Cases 310]; Garza v. Workmen's Comp. Appeals Bd. (1970) 3 Cal.3d 312 [35 Cal.Comp.Cases 500]; LeVesque v. Workmen's Comp. Appeals Bd. (1970) 1 Cal.3d 627 [35 Cal.Comp.Cases 16].) To constitute substantial evidence "... a medical opinion must be framed in terms of reasonable medical probability, it must not be speculative, it must be based on pertinent facts and on an 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).) "Medical reports and opinions are not substantial evidence if they are known to be erroneous, or if they are based on facts no longer germane, on inadequate medical histories and examinations, or on incorrect legal theories. Medical opinion also fails to support the Board's findings if it is based on surmise, speculation, conjecture or guess." (Hegglin v. Workmen's Comp. Appeals Bd. (1971) 4 Cal.3d 162, 169 [36 Cal.Comp.Cases 93].)

  The WCJ's decision was found not based on substantial evidence due to incomplete record and insufficient medical opinion support.

  Official decision · page 7 →
• ADJ8423470 · 2026-06-05 · Van Nuys District OfficeEscobedo

  Determinative passage · p.11An award, order or decision by the Appeals Board must be supported by substantial evidence in light of the entire record. (Lab. Code § 5903, 5952; Garza v. Workmen's Comp. App. Bd. (1970) 3 Cal.3d 312, 317-319 [33 Cal.Comp.Cases 500]; LeVesque v. Workmen's Comp. Appeals Bd. (1970) 1 Cal.3d 627, 635-637 [35 Cal.Comp.Cases 16].) To be considered substantial evidence, a medical opinion must be framed in terms of reasonable medical probability, it must be based on an adequate examination and history, and it must set forth reasoning to support the expert conclusions reached. (E.L. Yeager Construction v. Workers' Comp. Appeals Bd. (Gatten) (2006) 145 Cal.App.4th 922, 928 [71 Cal.Comp.Cases 1687]; Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604 (Appeals Bd. en banc).)

  The medical opinions of Drs. Kanter and Einbund met these criteria and were relied upon by the WCAB.

  Official decision · page 11 →
• ADJ14744840 · 2026-06-04 · San Francisco District OfficeEscobedo

  Determinative passage · p.13To constitute substantial evidence "... a medical opinion must be framed in terms of reasonable medical probability, it must not be speculative, it must be based on pertinent facts and on an adequate examination and history, and it must set forth reasoning in support of its conclusions." (Escobedo, supra.) "Medical opinion... fails to support the Board's findings if it is based on surmise, speculation, conjecture or guess." (Hegglin v. Workmen's Comp. Appeals Bd. (1971) 4 Cal. 3d 162, 169 [36 Cal.Comp.Cases 93, 97].)

  The Board rejected medical opinions that were speculative or conclusory, requiring substantial evidence for findings.

  Official decision · page 13 →