The situation that describes a violation of the due process clause under the Fourteenth Amendment is:
"The police performed a search on Stanley’s house for illegal substances even though they did not have a search warrant. When they found a trunk full of illegal substances, they arrested Stanley."
This scenario constitutes a violation of due process because the police conducted a search without a warrant, which is generally required to ensure that individuals' rights are protected against unreasonable searches and seizures, as established in the Fourth Amendment, which is applicable to the states through the Fourteenth Amendment.