If letters and private documents can thus be seized and held and used in evidence against a citizen accused of an offense, the protection of the Fourth Amendment declaring his right to be secure against such
searches and seizures is of no value, and, so far as those thus placed are concerned, might as well be stricken from the Constitution... The tendency of those who
execute the criminal laws of the country to obtain conviction by means of
unlawful seizures and enforced confessions, the latter often obtained after subjecting accused persons to unwarranted practices destructive of rights secured by the Federal Constitution, should find no sanction in the judgments of the courts which are charged at all times with the support of the Constitution and to which people of all conditions have a right to appeal for the maintenance of such fundamental rights.