S.D. Codified Laws § 43-30 app. 7-03
An instrument executed by a person who is a stranger to the record chain of title at the time such instrument is recorded does not make the title unmarketable, unless recently recorded, in which event some inquiry may be justified.
A title examiner should take notice of the interest of a person joining with the record owner in a contract, mortgage, lease, plat or easement, other than a spouse joining for possible homestead interest. Conveyances by strangers to the chain of title may be disregarded, unless a title examiner has actual notice of knowledge (through sources other than the record) of the interest of the grantor, or unless subsequent to such conveyance there is recorded a deed or other conveyance vesting title in such stranger.
SDCL app TO CHAPTER 43-30 § 7-03