What key aspect defines the 'Silver platter doctrine' that was terminated by Mapp v. Ohio?

The 'Silver platter doctrine' refers to a legal principle that allowed federal courts to admit evidence obtained by state law enforcement officers in violation of the Fourth Amendment, provided that the state officers were acting in good faith. This doctrine was based on the idea that while the states could obtain evidence using methods that were deemed illegal under federal standards, that same evidence could still be used in federal prosecutions as if it had been "served on a silver platter."

The case of Mapp v. Ohio in 1961 was pivotal because it ruled that evidence obtained in violation of the Fourth Amendment cannot be used in state courts, effectively terminating the Silver platter doctrine. The ruling emphasized the necessity for adherence to constitutional protections against unreasonable searches and seizures, which applies to both state and federal authorities.

In summary, the correct choice is about the ability of federal agents to utilize evidence obtained through illegal means by state agents, which was the crux of the Silver platter doctrine, and this was overridden by the Mapp v. Ohio ruling, reinforcing the principle that all evidence must be obtained lawfully regardless of the level of law enforcement involved.