California Code, Government Code - GOV § 20639

The compensation earnable during any period of service as a member of the Judges' Retirement System, the Judges' Retirement System II, the Legislators' Retirement System, or the Defined Benefit Program of the State Teachers' Retirement Plan shall be considered compensation earnable as a member of this system for purposes of computing final compensation for the member, if he or she retires concurrently under both systems.

A member shall be deemed to have retired concurrently under this system and under the Defined Benefit Program of the State Teachers' Retirement Plan, if the member is enrolled as a disabled member under the Defined Benefit Program of the State Teachers' Retirement Plan and for retirement under this system on the same effective date.