1970 the U.S. Supreme Court rendered a crucial decision in the case of Griggs v. Duke Power Co., an early employment discrimination case in which the court ruled unanimously that under Title VII of the 1964 Civil Rights Act, any screening device that produced unequal consequences for different races (i.e., what in employment law came to be known as "disparate impact" in the sense of disproportionate group harm) would be held to constitute individual employment discrimination unless the screening devices were shown to be clearly job-related. Four years after Griggs, the court reaffirmed its support for the "disparate impact" approach in Albemarle Paper Company v. Moody, a case in which employers sought to protect themselves against discrimination charges by hiring enough minorities to counteract any statistical charges of racial imbalance.

Nevertheless, a year later in Washington v. Davis, the court refused to extend the theory of disparate impact developed in Title VII cases to discrimination cases brought under the Equal Protection provisions of the U.S. Constitution. The court held that to establish a constitutional claim of unequal treatment (as opposed to a statutory claim of discrimination under Title VII), there had to be a showing of intent to discriminate, not simply a showing of disparate impact. At the time, the case was brought before the federal courts, Title VII, which would later be expanded in scope, did not cover municipal employees.

In 1989, the court, reflecting the more politically conservative influence of justices appointed by President Ronald Reagan, shifted the burden of proof in disparate impact cases from businesses to plaintiffs, making it more difficult to sustain an employment discrimination claim under Title VII. In Ward´s Cove packing v. Atonio and Price Waterhouse v. Hopkins the court ruled, “A simple statistical comparison of racial percentages between skilled and unskilled jobs was insufficient to make a prima facie case” of employment discrimination. In Price Waterhouse, the court shifted the burden of proof even further by requiring the plaintiff to prove that "employment practices substantially depended on illegitimate criteria".