The 4th: Independent source

“The independent source doctrine does not rest upon such metaphysical analysis, but upon the policy that, while the government should not profit from its illegal activity, neither should it be placed in a worse position than it would otherwise have occupied. So long as a later, lawful seizure is genuinely independent of an earlier, tainted one (which may well be difficult to establish where the seized goods are kept in the police's possession) there is no reason why the independent source doctrine should not apply.”

Murray v. United States, 487 U.S. 533, 542 (1988).