We demonstrate that cognitive constraints produce injustice in its most paradigmatic form: incorrect verdicts in judicial trials. Responding to a request for help, we conducted a field study in Mexican labor courts in which time pressure on the judges leads to their making mistakes, many of which are appealed. All we did was to index pages to random case files to help judges quickly find relevant information. We made no other changes whatsoever. Our treatment greatly reduced successful appeals, fully 50% in complex cases, and resulted in judicial opinions that were shorter and more on point. These findings have already informed recent reforms in Mexico‘s labor court procedures and have broader applicability.