Under California Civil Code Section 1710.2, if someone dies on the property, it's a material defect – but only if the death occurred within three years of the date you make an offer to purchase or rent the home. Technically, if the property was the location of a mass murder in 1975, the seller, lessor, agent or broker does not legally have to volunteer the information.
CCCS 1710.2 makes an exception for deaths caused by acquired immune deficiency syndrome. Federal law classifies AIDS as a disability, so disclosure of someone's death due to this cause is considered discriminatory. California law also provides that if you actually ask the seller or lessor about deaths that may have occurred on the property, the owner can't lie. The California Association of Realtors recommends that their agents come clean if questioned, no matter how long ago the death occurred. This doesn't hold true for AIDS-related deaths, however.
Jul 22, 2014