Citation Data Gets Richer

This is a guest post by Matt Dahl, a Ph.D. student in political science at the University of Notre Dame.

Authorities sidebar with citation counts

Citation data is a keystone of legal research—both for understanding a particular judicial decision and for discovering similar ones. However, binary information about whether one opinion cites another can only tell us so much.

Therefore, today I’m excited to announce that CourtListener is now calculating and making available a much richer metric of inter-opinion connectedness. Today we are introducing citation depth to indicate how many times every opinion cites another.

This means that in addition to recognizing and recording “full” citation references—e.g., Bush v. Gore, 531 U.S. 98—CourtListener is now parsing and counting the following kinds of citations as well:

  • Short form citations (e.g., 531 U.S., at 99)
  • Supra citations (e.g., Bush, supra, at 100)
  • Id. citations (e.g., Id., at 101)
  • Ibid. citations (i.e., Ibid.)

Because these abbreviated citations lack the detailed information contained in a full citation, they can be tricky to count correctly. Thus, this upgrade represents a major advance in CourtListener’s citation-detection abilities, and brings us closer to feature parity with commercial legal research …

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Citation Alerts are Better than Ever

How to create citation alerts

Back in 2016 we mentioned in a blog post that you can set up alerts to learn about new references to opinions in CourtListener. We called it: “Citation Alerts”, but they were a bit difficult to set up. Today we’re announcing that we’ve revamped Citation Alerts so they’re more obvious, easier to create, and easier to modify.

Citation Alerts are a wildly powerful feature that can be used to stay apprised of changes in the law. Basic Citation Alerts will send you an email when there’s a new cite to an opinion you’re following, but you can take them much further.

For example, let’s say you want to follow citations to Citizens United v. FEC. Doing that is really easy. Just open the case on CourtListener and on the left you’ll see a link for creating an alert. Click it and you’re all set.

But that’s only the beginning. Since 2010, Citizens has been cited about 650 times. That translates to more than one email a week. That’s probably too much clutter in your inbox, but you can prevent this by refining your alert. How about only citations from federal …

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We’ve Added Thousands More Citations to Historical Supreme Court Opinions

We have a small update to share today, as we’ve wrapped up adding thousands of historical Supreme Court citations to our collection. These are the original citations for the Supreme Court from 1754 to 1874, from before when the United States Reports had begun. Previously we had many of these citations, but as of today we can say we have historical citations for our entire SCOTUS collection.

For the unfamiliar, Supreme Court citations were originally named after the Reporter of Decisions for the Supreme Court from the time the opinion was published. For example, the first person to do this was Alexander Dallas, and his citations start at 1 Dall. 1 (1754), and go forward to 4 Dall. 446 (1806). After Dallas came a long line of other reporters, each of whom named their series of books after himself until 1875, when congress began appropriating money for the full time creation of these reporters and demanded they be called the “United States Reports.”

18 Stat. 204 (1874)

A snapshot of 18 Stat. 204 (1874), which allocated $25,000 to the Supreme Court for printing (about $557,100 today).

At that time, 91 U.S. 1 was the first case to be born with …

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Some Citation Parsing Statistics

We want to share some quick statistics today. We we just completed running our citation parser across the entire CourtListener collection. If you follow our work, you’ll know that the purpose of the citation parser is to go through every opinion in CourtListener and identify every citation from one opinion to another (such as “410 U.S. 113“). Once identified, the parser looks up the citation and attempts to make a hyperlink between the opinions so that if you see a citation while reading, you can click it to go to the correct place.

As you can imagine, looking up every citation in every opinion in CourtListener can take some time, so we only run our citation finder when we need to. In this case:

  • The process ran continuously for two weeks.
  • It ran a total of 253,872,460 queries against our search engine.
  • It found 25,471,410 citations between opinions.
  • There are about three million opinions currently in CourtListener.

After running the parser, the first stop I like to take is to go and see the search results ordered by citation count. In an upset, Strickland v. Washington, the former leader, has been pushed to third …

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Citation Searching on CourtListener

One of the great new features that the new version of CourtListener provides is what we’re calling Citation Searching. Citation Searching lets you look at all the opinions that cite an opinion you’re interested in and then slice and dice them so that you only see the ones that are important to you.

For example, say you’re looking at Roe v. Wade and you want to analyze the cases that have cited it. In CourtListener, in the sidebar on the left, there’s a list of the opinions citing the one you’re looking at, in the section called “Cited By”. At the bottom of that section, there’s a link that says, “Full List of Cited Opinions”.

Sidebar

If you click that link, you’ll be taken back to the search results page, and you’ll see that your query is for cites:(108713). The number in there is the ID of Roe v. Wade that you can see in its URL. This is just standard CourtListener search syntax, so you can tweak it however you like.

For example, another important case in this area is Planned Parenthood v. Casey, which has an ID of 112786. If …

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