Abstract This study sought to determine the influence of technical expertise on judgments rendered in social security lawsuits at federal courts and judgeships in Rio de Janeiro city (RJ), Brazil. To this end, 431 legal proceedings completed between 2018 and 2020 were qualitatively and quantitatively analyzed. After classification as to medical specialty demanded in lawsuits and request successes, the expert reports were directly compared with court decisions. In conclusion, technical evidence showed to be essential for Social Security Law and is the main influence on court decisions. When there was no such direct influence, procedural, legal, or social issues expressly described by law had supremacy.