common source doctrine
common-source doctrine. The principle that a defendant in a trespass-to-try-title action who claims under a source common to both the defendant and the plaintiff may not demonstrate title in a third source that is paramount to the common source because doing so amounts to an attack on the source under which the defendant claims title. [Cases: Trespass to Try Title 11. C.J.S. Trespass to Try Title § 17.]
