A more thorough explanation:

The Silver-Platter Doctrine was a principle in criminal procedure that allowed a federal court to admit evidence obtained illegally by a state police officer, as long as a federal officer did not participate in or request the search.

For example, if a state police officer conducted an illegal search and seizure and found incriminating evidence, they could turn that evidence over to federal authorities who could then use it in court under the Silver-Platter Doctrine.

However, in 1960, the Supreme Court rejected this doctrine in the case of Elkins v. United States. The Court ruled that evidence obtained illegally by state officers could not be used in federal court, even if a federal officer was not involved in the search.

Overall, the Silver-Platter Doctrine was a controversial legal principle that allowed for the admission of illegally obtained evidence in certain circumstances, but it has since been overturned by the Supreme Court.