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But some academics are claiming, based on a new type of research called “corpus analysis,” to have found fresh evidence that Scalia was wrong. “Bearing arms,” they say, overwhelmingly referred to military service in the Founding era, rather than simply referring to the carrying of weapons. These scholars further suggest that Heller might have been wrong more deeply — even when it comes to keeping arms — though that is not the focus of the current case (and their “bear arms” argument is generally recognized as their strongest).

In corpus analysis, researchers start with a massive collection of writings or speech from a given time period (a “corpus”) and search it for uses of a contested term. They can look at how the term was used in context and count up how many times it was used in various ways. The potential appeal to constitutional originalists, who want laws to be interpreted by their “original public meaning” — the way an ordinary person would have read them at the time they were enacted — is obvious. This is, after all, a look at how people actually used words across a wide range of contexts.

When a court interprets a tricky term, the question is often whether the term’s “ordinary” meaning is broad enough to cover some disputed conduct. But corpus analysis doesn’t tell us that. What it tells us, instead, is how frequently people actually use the term to refer to the conduct in question, relative to how often they use the term in other ways. This number is not necessarily all that informative.

As Josh Blackman and James C. Phillips once noted, for example, if you checked a corpus for uses of the verb “to read,” you’d probably find far more examples of people reading newspapers than of people reading street signs — but the low frequency of street-sign references would tell you nothing of importance. It would merely reveal that people read newspapers more than they read street signs, or at least more frequently discuss reading newspapers. A law forbidding people “to read,” or a constitutional provision giving them a right to, would presumably apply to street signs (and nutritional labels and ancient scrolls) just as much as it applied to newspapers.

This problem is compounded by the fact that corpus analysis systematically produces narrow senses of what a term means, as a paper in the Harvard Law Review last year by Kevin P. Tobia showed.

In a series of experiments run on ordinary people, law students, and judges, Tobia divided his subjects into three groups. One group was simply given a term (say, “vehicle”) and asked whether various things counted as part of the category (cars, airplanes, shoulder baby carriers, etc.), to gauge the scope of the term’s ordinary meaning. The other two groups, by contrast, were not given the actual word, so they wouldn’t rely on their preexisting sense of what the word meant. Instead, they were given a fake word (such as “ailac”), accompanied by either (A) a dictionary definition of the real word Tobia was testing or (B) some results from a corpus analysis of that word, including examples of the word used in context and other terms the word was frequently used alongside.

The upshot of these experiments is that corpus analysis tends to highlight a narrow subset of a term’s potential uses. Those relying on corpus results, for example, tended to say that an airplane does not count as a vehicle (or rather, as an “ailac”), contrary to the folks who were asked to rely on their own sense of the word. Originalist fans of dictionary definitions shouldn’t take any comfort in the study, either: Those relying on dictionary definitions tended to have an especially broad sense of the tested word, saying, for instance, that a shoulder baby carrier is a vehicle.