The Court operates under the doctrine of stare decisis. That's Latin for "to stand by that which is decided." In other words, a court decision sets a precedent, that is then applied to subsequent cases, as applicable.
But that's not an absolute rule to be applied to all cases. Sometimes, the Supreme Court changes its collective mind, over time. Two examples:
In the 1896 case of Plessy v. Ferguson, the Court ruled that separate railway cars for black and white passengers did not violate the 14th Amendment's guarantee of equality. The Louisiana statute in question provided for "equal but separate accommodations for the white and colored races".
As the sole dissenter, Associate Justice John Marshall Harlan (grandfather of the John Marshall Harlan who served on the Court from 1955 to 1971) wrote:
The arbitrary separation of citizens on the basis of race while they are on a public highway is a badge of servitude wholly inconsistent with the civil freedom and the equality before the law established by the Constitution. It cannot be justified upon any legal grounds.
58 years later, Chief Justice Earl Warren wrote, with the concurrence of a unanimous Supreme Court, that:
... in the field of public education, the doctrine of "separate but equal" has no place. Separate educational facilities are inherently unequal.
The Warren Court dealt with the same issue of racial segregation that was addressed in the Plessy case. But, in 1954, the context was public schools, and the case was Brown v. Board of Education.
In Brown, Warren and his colleagues very specifically declared that they were repudiating their predecessors' Plessy decision. Subsequent case law and legislation extended that repudiation of segregation to areas other than education.
Another subject on which the Supreme Court reversed itself involved the so-called "sodomy laws", i.e., state statutes that outlawed sexual activity other than heterosexual vaginal intercourse.
By 1986, many states had repealed those laws. But some states, including Georgia, still had them on the books. In the case of Bowers v. Hardwick, the Supreme Court that year upheld the constitutionality of Georgia's sodomy law.
Those of us who opposed the Bowers result, despaired over the prospects for overturning the decision. We knew that African Americans had waited 58 years for the Court to move from Plessy to Brown.
But things move faster nowadays, and the Supreme Court overturned its Bowers decision in 2003, when it struck down a Texas sodomy law in the case of Lawrence v. Texas. I'll have more to say about Lawrence as I trace the development of the right to privacy, in future posts.
I'll also discuss a decision, the opponents of which have looked in vain for a reversal: the 1973 Roe v. Wade abortion decision.