From the ABA Journal:
The U.S. Supreme Court has cited Internet materials 555 times since 1996, but tracking down the information isn’t always easy.
According to a new study by co-authored by Harvard law professor Jonathan Zittrain, half of the hyperlinks in Supreme Court opinions no longer link to the information originally cited. The New York Times covers the results. “Supreme Court opinions have come down with a bad case of link rot,” the Times says.
According to the study, many of the links did turn up Web pages, but
they didn’t go to the original information cited or the information had
materially changed. Sometimes when the information changed, there was no
note indicating the update.
The Times notes one hyperlink in an opinion about violent video games
by Justice Samuel A. Alito Jr. Users who click on the link are taken to
an error message
that reads: “Aren’t you glad you didn’t cite to this Web page? … If you
had, like Justice Alito did, the original content would have long since
disappeared and someone else might have come along and purchased the
domain in order to make a comment about the transience of linked
information in the Internet age.”
The Supreme Court clerk does keep a hard copy of hyperlinked
materials, but Zittrain suggest another solution: a platform that would
allow authors to generate, store, and reference archived data. He is
working on such a platform, called Perma.cc, which is supported by a
group of law libraries and nonprofits. Though the project would
initially focus on legal scholarship, it would also work for the Supreme
Court, Zittrain told the Times.
Source: Debra Cassens Weiss, Link Rot in SCOTUS Decisions Documented; Half Don't Go to Original Material, ABA Journal (Sep. 24, 2013).
Jonathan Zittrain, Perma: Scoping and addressing the problem of "link rot," The Future of the Internet and How to Stop It (Sep. 20, 2013).
Kendra Albert & Jonathan Zittrain, Perma: Scoping and Addressing the Problem of Link and Reference Rot in Legal Citations (working paper on SSRN) (Sep. 21, 2013).
Adam Liptak, In Supreme Court Opinions, Web Links to Nowhere, N.Y. Times (Sep. 23, 2013).
Raizel Liebler & June Liebert, Something Rotten in the State of Legal Citation: The Life Span of a United States Supreme Court Citation Containing an Internet Link (1996—2010), 15 Yale J.L & Tech. 273 (2013)
Perma.cc, a service, currently in beta, that allows users to create citation links that will never break.