California Code, Labor Code - LAB § 4753

Such additional compensation is not in addition to but shall be reduced to the extent of any monetary payments received by the employee, from any source whatsoever, for or on account ofsuch preexisting disability or impairment, except as to payments being made to the employee or to which he is entitled as a pension or other compensation for disability incurred in service in the armed forces of the United States, and except as to payments being made to him or to which he is entitled as assistance under the provisions ofChapter 2 (commencing with Section 11200), Chapter 3 (commencing with Section 12000), Chapter 4 (commencing with Section 12500), Chapter 5 (commencing with Section 13000), or Chapter 6 (commencing with Section 13500) of Part 3, or Part 5 (commencing with Section 17000), of Division 9 of the Welfare and Institutions Code, and excluding from such monetary payments received by the employee for or on account ofsuch preexisting disability or impairment a sum equal to all sums reasonably and necessarily expended by the employee for or on account of attorney's fees, costs and expenses incidental to the recovery of such monetary payments.

All cases under this section and under Section 4751 shall be governed by the terms of this section and Section 4751 as in effect on the date of the particular subsequent injury.