A Special Warranty Deed only provides warranty of title for the period during which the grantor owned the property. In some jurisdictions that type of deed is called a quitclaim deed. It does not guarantee that the grantor has good title, full ownership or that there exist no liens or defects prior to the grantor's ownership.
If you acquire real property by a Special Warranty Deed you should have the title examined by a professional title examiner who is familiar with the required time period that must be covered by a title examination in your state as well as ALL the legal issues that affect title to real property. An attorney should represent you in the purchase.