In US law, the independent source doctrine is an exception to the exclusionary rule. The doctrine applies to evidence initially discovered during, or as a consequence of, an unlawful search, but later obtained independently from activities untainted by the initial illegality.
The United States Supreme Court, in Nix v. Williams, provided the policy rationale for admitting tainted evidence:
The independent source doctrine teaches us that the interest of society in deterring unlawful conduct and the public interest in having juries receive all probative evidence of a crime are properly balanced by putting the police in the same, not a worse, position that they would have been in if no police error or misconduct had occurred.