Cal. CIV § 1942.3

(a) In any unlawful detainer action by the landlord to recover possession from a tenant, a rebuttable presumption affecting the burden of producing evidence that the landlord has breached the habitability requirements in Section 1941 is created if all of the following conditions exist:

(1) The dwelling substantially lacks any of the affirmative standard characteristics listed in Section 1941.1, is deemed and declared substandard pursuant to Section 17920.3 of the Health and Safety Code, or contains lead hazards as defined in Section 17920.10 of the Health and Safety Code.

(2) A public officer or employee who is responsible for the enforcement of any housing law has notified the landlord, or an agent of the landlord, in a written notice issued after inspection of the premises which informs the landlord of his or her obligation to abate the nuisance or repair the substandard or unsafe conditions identified under the authority described in paragraph (1).

(3) The conditions have existed and have not been abated 60 days beyond the date of issuance of the notice specified in paragraph (2) and the delay is without good cause.

(4) The conditions were not caused by an act or omission of the tenant or lessee in violation of Section 1929 or 1941.2.

(b) The presumption specified in subdivision (a) does not arise unless all of the conditions set forth therein are proven, but failure to so establish the presumption shall not otherwise affect the right of the tenant to raise and pursue any defense based on the landlord’s breach of the implied warranty of habitability.

(c) The presumption provided in this section shall apply only to rental agreements or leases entered into or renewed on or after January 1, 1986.