In California, whose name appears on the deed is the beginning of the inquiry, not the end of the story. There is often a significant community property interest in real property even if it was purchased prior to marriage and title is held as the "sole and separate property" of one of the parties.
Community Property Interest in Property purchased prior to marriage by one spouse as that spouse's "sole and separate" property. If the community pays down the mortgage balance, or the property is refinanced during marriage, the community will obtain an interest in separate property purchased prior to marriage as the "sole and separate" property of one spouse. If one of the spouses brings to the marriage a residence that is subject to an encumbrance, and the encumbrance is paid in whole or in part with community property during the marriage, the property, while remaining separate, will develop a community property interest that must be divided. The calculuation of this interest is sometimes referred to as the Moore-Marsden interest in the property.
Source: http://www.attorneyincourt.com/MoreInfo_RealProperty.htm
