The only way to carry the burden of proof is to present evidence. This evi- dence can contain conflicts and unclarities, which make it hard to prove the facts. Sometimes the facts are so complex that they simply cannot be proved one way or the other, and sometimes the distinction between facts and law is not so clear.
These problems arise often in cases that raise larger social issues. For exam- ple, in the famous case of Brown v. Board of Education, which found segregated schools unconstitutional, the Supreme Court an- swered the question of law at issue by saying “the opportunity of an education . . . is a right which must be available to all on equal terms.” The Court next asked: “Does segregation of children in public schools solely on the basis of race . . . deprive the children of the minority group of equal educational oppor- tunities?” This question was presented as a question of fact. The Court an- swered in the affirmative and tried to justify its answer by citing various psychological studies of the performance of minority children from segregated schools. This answer would be accepted by most people today, but the studies used as proof were controversial and inconclusive, so the Court had to decide whether studies of this kind were reliable enough to serve as evidence in this case. Moreover, the answer to the above question also depends on what counts as “equal educational opportunities” for the purposes of the law. For example, the studies cited by the Court found that segregated schools “affect the moti- vation of a child to learn,” but these factual studies could not determine whether lowered motivation to learn counts as lowered opportunity to learn. The Court had to decide this issue because it in effect determines what the law is— what it prohibits and what it allows. Thus, what was presented as a question of fact turned out to be at least partly a question of law. In such cases, it is not clear where law ends and facts begin.