Obiter dictum is something that is said in passing. It is an observation or opinion of the court but one not necessary to the decision at hand. It is sometimes a persuasive point but not relevant to the issue decided.
Mr. Chief Justice Taney writing for the Supreme Court in Dred Scott v. Sanford—one of the gravest errors in American legal history--stated: 'this court has decided against the jurisdiction of the circuit court…and if anything it may say upon that part of the case will be extra-judicial, and mere obiter dicta." Dred Scott brought a lawsuit for his freedom in the Circuit Court of St. Louis County, Missouri. He received a verdict in his favor, granting him his freedom, but this decision was deemed
obiter dicta because a black person in 1856 was not recognized as a citizen of the United States and consequently was denied the right to bring a lawsuit.
The obiter dictum in Dred Scott became the basis for the XIV Amendment ratified on July 9, 1868. "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and any of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person visits in its jurisdiction the equal protection of the laws."
Obiter dictum is pronounced (ob-i-ter