2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/224228We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve explicit concomitants of the Riemann tensor.15 pages; v2: necessary conditions added to theorems 1 and 2, other minor changesGeneral Relativity and Quantum Cosmologytext