The LLT Lab empirically investigates the argument structures actually found in legal documents, with the goal of developing a useful theory of legal reasoning in general. Traditional treatments of formal logic have been inadequate as theories of legal reasoning for several reasons. One is that formal patterns of reasoning developed in the abstract tend to represent very little of the natural language patterns found in actual documents. Another is that such theories do not provide useful heuristics for proceeding from sentences in text to argument structures. The Lab addresses both of these problems by proceeding from actual texts to develop patterns that explain all or most of the text. This general theory of legal reasoning draws upon our investigations within specific legal domains, such as vaccine-injury compensation decisions and medical malpractice decisions.