Special creationism is the belief that God directly intervened to create the different kinds of life and humans in particular. Legal bans on teaching evolution were struck down by the US Supreme Court in 1968, which held that such laws unconstitutionally impose religious views on public school students. In response, creationists concocted "creation science," an attempt to justify supposedly Biblical ideas like a 6,000-year-old earth, Noah's ark, and the special creation of life by using arguments that appeared superficially scientific.
Laws requiring the teaching of “creation science” were evaluated by the federal courts in the 1980s, and two courts, first in Arkansas and then in Louisiana, ruled that these policies were unconstitutionally religious. Two years after the Supreme Court struck down laws requiring the teaching of "creation science" in public schools, the first ID textbook was published.
In a 2005 federal court case, Kitzmiller v. Dover, early drafts of the textbook were subpoenaed and provided to Barbara Forrest, a scholar who researches the ties between ID and its earlier creationist ancestors, and who published that research in Creationism's Trojan Horse. Her investigation of early drafts of the ID textbook and NCSE's archives showed that the book began as a "creation science" textbook. As described in the video below, her research showed that the authors performed a global search and replace on the text in the months following the Supreme Court ruling on "creation science," replacing "creation" with "design."
The judge in the Kitzmiller case was not impressed by the attempt to sidle around the Supreme Court's ruling, and ruled that the history and content of the textbook, and of ID in general, are not legally distinct from "creation science" or other forms of special creationism. In this and a host of other ways, modern ID is simply a new gloss on long-discredited creationist views, and has no more merit than they did.