The home was not habitable
If the landlord failed to fix serious problems you did not cause, such as no heat, leaks or broken locks, that can be raised in an eviction for unpaid rent under Civil Code section 1941.1 and Code of Civil Procedure section 1174.2.
The eviction is retaliation
Civil Code section 1942.5 protects tenants who complained about conditions or contacted a code enforcement agency. An eviction within 180 days of that activity deserves close scrutiny.
The notice was defective
A notice that overstates the rent, adds charges that are not rent, gives too little time or was served improperly may not support an eviction.
Just cause and rent limits under the Tenant Protection Act
For many tenants of 12 months or more, Civil Code section 1946.2 requires a just cause to end the tenancy, and section 1947.12 caps rent increases. Some housing is exempt.
Los Angeles rent control and the Just Cause Ordinance
In the City of Los Angeles, the Rent Stabilization Ordinance generally covers rentals built on or before October 1, 1978, and the Just Cause Ordinance covers most other rentals after six months or once the original lease expires. Both limit the reasons for eviction and require relocation assistance for no fault evictions. A covered tenant generally cannot be evicted for unpaid rent unless the amount owed exceeds one month of Fair Market Rent for the unit size.
Discrimination
California fair housing law prohibits evictions based on race, national origin, disability, familial status, source of income such as a housing voucher, and other protected traits.