In California, a county assessor's office updates the property assessment rolls listing the value and ownership of each property once a year. The information is posted publicly on July 1.
An assessor's office also will then update its records when a property is sold to reflect the new assessed value and change of ownership.
But there may be a lag time before this information is entered into the publicly accessible database on property ownership. So check with the assessor's office to determine how up to date the ownership records are.
To verify the current owner of a piece of property you should check the county recorder's office where property transactions are recorded daily.
The recorder's office has an index of property related transactions organized alphabetically by the names of the people or companies involved in the transactions, such as the names of the buyer and seller of a piece of property.
Thus you can take the name of a property owner listed at the assessor's office and check that name at the recorder's office to see if a property deed has been filed showing the property was recently sold to someone else.