The case "Washington, Mayor of Washington, D.C., et al. v. Davis et al." involved a written test called "Test 21" used for police recruit applicants in the District of Columbia. Two Black police officers filed a lawsuit alleging racial discrimination in promotion policies, and two other Black applicants intervened, claiming that the recruitment procedures, including the written test, discriminated against Black applicants. The District Court upheld the test, but the Court of Appeals invalidated it, citing a violation of the Fifth Amendment due process clause. However, the Supreme Court reversed the judgment of the Court of Appeals and agreed with the District Court that the test was not unlawfully discriminatory under the Fifth Amendment.

The Supreme Court clarified that a law or official act is not unconstitutional solely because it has a racially disproportionate impact, without regard to whether it reflects a racially discriminatory purpose. Discrimination must be proven through systematic exclusion or unequal application of the law. Discriminatory purpose can be inferred from the systematic exclusion of a particular race from juries or from racially non-neutral selection procedures. Disproportionate impact alone does not trigger strict scrutiny of racial classifications. The Court held that the operative effect of the law, rather than its purpose, is the paramount factor. However, the prevailing rule is that purposeful discrimination is the principal issue in equal protection litigation.

The court rules that Test 21 is not discriminatory, even if it disproportionately affects a particular racial group, as it assesses necessary verbal skills and serves a valid purpose. The lower court erred in granting summary judgment based on the Fifth Amendment, and the Court of Appeals should have affirmed the judgment of the District Court. Justices Brennan and Marshall dissent from the Court's holding. However, the District Court's conclusion that Test 21 is valid for predicting success in police training contradicts CSC guidelines and EEOC regulations. The Court's conclusion conflicts with EEOC regulations and previous cases such as Griggs and Albemarle. The petitioners have not provided enough evidence to support their case, so the judgment of the Court of Appeals should be upheld.