Witnessing can assume many different forms including religious, literary, and legal versions. This chapter begins by focusing on examples of textual witnessing such as the sourcebooks of Tcherikower and Dubnow mentioned in Chapter 2 in which the compilers assembled troves of documents as a form of historical proof. The focus then shifts from the first to the second half of the twentieth century by discussing instances in which historians are called upon to take the stand in legal cases. The chapter explores a range of cases related to the Holocaust in which historians played important roles as witnesses, particularly the Eichmann trial in Jerusalem in 1961 in which historian Salo W. Baron was a key witness. The chapter concludes by discussing the libel trial brought by David Irving against Deborah Lipstadt in London in 2000 in which a “dream team” of historians, including Richard Evans and Christopher Browning, served as defense witnesses. The victory of Lipstadt’s side proved to be a vindication for memory, as well as history, and, as such, an indication of the somewhat porous boundary between them.