John Marshall Harlan II was a justice of the Supreme Court of the United States from 1955 to 1971. His grandfather was John Marshall Harlan, also a Supreme Court justice who served from 1877 to 1911 and was the famous sole dissenter in Plessy v. Ferguson.

Harlan served as a judge in the United States Court of Appeals for the Second Circuit from 1954 to 1955. In 1955, he was nominated by President Dwight D. Eisenhower to the Supreme Court and was confirmed by the Senate.

During his tenure on the Supreme Court, Harlan was very conservative, arguably the most conservative justice during the Warren Court. He dissented in many cases giving criminal defendants procedural safeguard, such as Miranda v. Arizona, a case that required the police to inform the criminal suspect's rights before questioning, and Mapp v. Ohio, a case that the majority of the court ruled that illegally obtained evidence cannot be used in a trial. He opposed incorporating the entire Bill of Rights to individual states. He also opposed the doctrine of "one man, one vote" in apportionment disputes.

However, Harlan did hold some views that are considered liberal in current standard, such as his support for the Substantive Due Process doctrine. He also supported racial equality and desegregation. He was authored the majority decision in Cohen v. California, a landmark free speech case.

Harlan retired from the court in 1971, and died in the same year.

Note: many facts in this writeup came from Wikipedia.