Statistical Proof - in Legal Proceedings

In Legal Proceedings

"Where gross statistical disparities can be shown, they alone may in a proper case constitute prima facie proof of a pattern or practice of discrimination."

Statistical proof in a legal proceeding can be sorted into three categories of evidence:

1. The occurrence of an event, act, or type of conduct,
2. The identity the individual(s) responsible
3. The intent or psychological responsibility

Statistical proof was not regularly applied in decisions concerning United States legal proceedings until the mid 1970's following a landmark jury discrimination case in Castaneda v. Partida. The US Supreme Court ruled that gross statistical disparities constitutes "prima facie proof" of discrimination, resulting in a shift of the burden of proof from plaintiff to defendant. Since that ruling, statistical proof has been used in many other cases on inequality, discrimination, and DNA evidence. However, there is not a one-to-one correspondence between statistical proof and the legal burden of proof. "The Supreme Court has stated that the degrees of rigor required in the fact finding processes of law and science do not necessarily correspond."

In an example of a death row sentence (McCleskey v. Kemp) concerning racial discrimination, the petitioner, a black man named McCleskey was charged with the murder of a white police officer during a robbery. Expert testimony for McClesky introduced a statistical proof showing that "defendants charged with killing white victims were 4.3 times as likely to receive a death sentence as charged with killing blacks.". Nonetheless, the statistics was insufficient "to prove that the decisionmakers in his case acted with discriminatory purpose." It was further argued that there were "inherent limitations of the statistical proof", because it did not refer to the specifics of the individual. Despite the statistical demonstration of an increased probability of discrimination, the legal burden of proof (it was argued) had to be examined on a case by case basis.