As you know by now, the U.S. legal system consists of dynamic norms which reflect social-economic changes as well as our changing mores. Like with statutory law, the final research step for case law research is making sure that subsequent law -- statutes or court decisions -- has not affected what you have deemed to be the applicable or just relevant decision.

Unlike statutes, decisional law has a different life span: it does not expire at a specific date in time, or in time. Cases can be directly affected when they are reversed, or modified by a subsequent decisions from the same or a superior court, or implicitly by statutory law. The first occurrence is the one that absolutely invalidates your legal research. The latter one only raises issues of concern.

For example, the U.S. Supreme Court held in Roe v. Wade, 410 U.S. 113 (1973), that all women had a “fundamental right” to choose to terminate their pregnancies absent a “compelling state interest” ( 410 U.S. at 155 et seq) The fundamental right to choose put together by the Supreme Court in Roe v. Wade was comprised of three components, for each trimester of pregnancy. The women had complete control over their pregnancy until viability-during their first trimester of pregnancy. Afterwards, during the following two trimesters of pregnancy, upon showing a compelling interest in the pregnancy, the state was allowed to interfere and issue
different state regulation that could have adversely impacted a woman’s right to decide the future of her pregnancy.

With respect to the State’s important and legitimate interest in potential life, the “compelling” point is at viability. This is so because the fetus then
presumably has the capability of meaningful life outside the mother’s womb. State regulation protective off life after viability thus has both logical and
biological justifications. If the State is interested in protecting fetal life after viability, it may go as far as to proscribe abortion during that period, except
when it is necessary to preserve the life or health of the mother. (410 U.S. 163-164)

However, the Roe v. Wade right to choose did not last long. The Court substantially altered it 20 years later in Planned Parenthood of Southeastern Pennsylvania v. Casey, 505 U.S. 833 (1992). In its new embodiment, the woman has no absolute right to choose during any time of the pregnancy: states could regulate a woman’s pregnancy and interfere with her own wishes before the viability point. In Casey, the Court held that a woman could still terminate her pregnancy before viability, (505 U.S. at 871), whether “viability occurs at approximately 28 weeks, [or] at 23 to 24 weeks” (Id., at 860), but that she had lost her complete control over her pregnancy during that period of time. The Court allowed the state to interfere and obstruct her potential desire to abort the fetus. The only limit the Court imposed was that the state could not pass legislation that would create requirements that would likely become a “substantial obstacle to the woman’s exercise of the right to choose” (Id., at 877).

If under Roe, the woman had more control, and the state’s interference was more limited, under Casey the woman’s prerogatives became less while the state’s interference increased. The state could pass rules about an informed consent requirement, mandatory 24-hour waiting periods, etc., meant to discourage women from aborting. For all these substantive reasons, you need to update your research. There are fast, fee-based, and easy to use ways which can help researchers make sure that their results is still good law. The fastest, most expensive and most reliable updating services are three: Shepards (Lexis), KeyCite (Westlaw), and, at a much cheaper rate, BCite ( Cheaper case law databases also provide a similar service by pointing out the cases citing your choice. It is then your duty to read all those citing cases and decide their subsequent validating impact on your research.

Unfortunately, not all state and federal cases are aggregated in one place. There is still to be done in terms of openlibrary movement when it comes to legal research.

Fortunately, when it comes to federal case law, remember that the United States Supreme Court case law is the law of the land. U.S. Supreme Court cases are open to few changes. Sometimes the U.S. Supreme Court reverses itself, or, in more often occurrences, it changes its approach to an issue, as it did with Roe in Casey. Moreover, in very rare occasion, as explained in the previous chapter, last section, will Congress enact a statute that will invalidate a Court’s decision.