“Sexed cow semen” is bull semen containing only X- or Y-chromosome-bearing sperm. It allows dairy farmers using artificial insemination to ensure they breed only female—and thus milk-bearing—cows. It’s valuable stuff, and, until recently, the U.S. market was controlled by a monopolist whose technology worked by identifying sperm cells, electrically charging them, and then sorting them with magnets. But when an upstart hired one of the monopolist’s ex-employees, she shared the monopolist’s trade secrets. The upstart then began using a different, potentially faster method: individually vaporizing the unwanted sperm cells with a laser millions of times per second. The ensuing antitrust/patent infringement/breach of contract suit, culminating in a two-week trial, gave wins and losses to both sides. On appeal, the Seventh Circuit affirmed some of the monopolist’s wins but also—in a complicated discussion of patent law featuring set theory, subscripted variables, and LSAT-esque diagrams—gave the upstart a second chance at invalidating the seminal patent claims.