McMicken v. United States was a United States Supreme Court case that dealt with the issue of whether a person could be convicted of a crime if the evidence used to convict them was obtained through an illegal search and seizure. The case involved a man named John McMicken, who was accused of stealing a horse. The police searched his home without a warrant and found evidence that he had committed the crime. McMicken argued that the evidence should not be used against him because it was obtained through an illegal search and seizure. The Supreme Court agreed with McMicken and ruled that evidence obtained through an illegal search and seizure could not be used to convict a person of a crime. This ruling established the exclusionary rule, which states that evidence obtained through an illegal search and seizure cannot be used in a criminal trial. The ruling in this case has been used in many subsequent cases to protect the rights of individuals from unreasonable searches and seizures.

In the case of McMicken v. United States, the Supreme Court was asked to decide whether a statute that allowed for an individual's property to be seized and sold in order to pay off their debts was constitutional. The majority opinion held that it was, but Justice Field dissented from this ruling. He argued that such a law violated both due process and equal protection under the Fourteenth Amendment because it did not provide any means by which debtors could challenge or appeal seizures of their property before they were sold off. Furthermore, he noted that while creditors had access to legal remedies if debtors failed to pay them back, there were no similar protections available for those who owed money when their assets were taken away without warning or recourse. In conclusion, Justice Field believed that such laws should only be applied after proper notice has been given and all reasonable attempts have been made at negotiation between debtor and creditor so as not to deprive individuals of their rights without due process of law.