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“Apportionment: Case Law Outline Focusing On Evolving Themes, Trends, and Problem Areas.”
(July 2022 Edition)


Raymond F. Correio, Senior Associate, Pearlman, Brown & Wax, LLP; Workers’ Compensation Judge (retired); Prior editions dated January 2021, July 2020, January 2020, July 2019, January 2019, January 9, 2017, (110 pages), April 2013 (67 pages), and January 2011 (120 pages) can be found at: www.PBWlaw.com under the “Resources” tab and the “Educational Materials” subtab.
© Copyright 2021, All Rights Reserved.



1. Fundamental Analytical Principles
2. Age, Gender, and Genetics
3. Risk Factors (Causation of Injury versus Causation of Permanent Disability)
4. The AMA Guides: Disability versus Impairment
5. Petitions to Reopen/Vargas
6. Benson
7. Medical Treatment and Apportionment
8. Medical Evidence of Apportionment and Vocational Evidence
9. Labor Code §4662(a)
10. Labor Code 4662(b)
11. Labor Code 4663
12. Labor Code 4664
13. Range of Evidence
14. Discovery
15. Table of Cases


The content of this case law summary is not intended to provide legal advice. Distribution and use of this material is for educational use only and is not intended as consideration for future
business. This document is the property of Pearlman, Brown & Wax and may not be further distributed without express written permission.

Fundamental Analytical Principles


In my 2013 Apportionment Case Law update I included for the first time a section dealing with “fundamental analytical principles,” based on the working assumption that it would provide an
ongoing resource to the workers’ compensation community as a reference and guide dealing with the critical underlying fundamental analytical concepts and principles related to Labor Code
§4663 and Labor Code §4664, as well as a separate commentary on substantial medical evidence and correct legal standards. In subsequent outlines I intentionally eliminated or removed this
section based on the belief that most, if not all, workers’ compensation practitioners, judges, and evaluating physicians for the most part understood the basic fundamental analytical principles
and concepts underlying the radical change in the law of apportionment effectuated by the passage of SB899 and Labor Code §§4663 and 4664.

However, in the intervening years since 2013, and after my review and analysis of numerous recent apportionment cases, it is abundantly clear that a significant number of practitioners and evaluating physicians still do not fully comprehend the fundamental core analytical principles and concepts essential to understanding the correct application of Labor Code §§4663 and 4664 and related substantial medical evidence standards.

Graphic examples to support my decision to include this section once again in the outline are exemplified by two recent cases, and numerous other recent cases, which clearly show a widespread misunderstanding of the fundamental principles underlying Labor Code §§4663 and 4664. In the case of Caires v. Sharp Health Care (2014) Cal.Wrk.Comp. P.D. LEXIS 145 (WCAB panel decision), three different evaluating physicians in the same case all failed to demonstrate a basic understanding of the core concepts and principles related to Labor Code §4663 apportionment. What is striking about the Caires case is the fact the apportionment issue was fairly straightforward, involving whether or not there was valid legal apportionment related to preexisting degenerative conditions. Caires also deals with an important issue related to whether the AMA Guides can be used by reporting physicians to determine valid legal apportionment under Labor Code §§4663 & 4664.

Perhaps a more graphic example is the very recent case of Pattiz v. SCIF/MTC Trucking, Inc. 2015 Cal.Wrk.Comp. P.D. LEXIS 541, 43 CWCR 201, in which a workers’ compensation judge in issuing a joint Findings of Fact and Award in two cases incorrectly dealt with four separate apportionment issues in the same case, including Benson, Labor Code §4663 nonindustrial apportionment, the interaction of medical evidence of apportionment and vocational evidence, and finally erroneously construed and applied the Labor Code §4662(b) determination of permanent total disability “in accordance with the fact.” (sic). The fact a judge ten years after


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