His hands extracted the DNA of Lasa and Zabala, of the terrorists from 11-M and of the victims of the Civil War buried in Cuelgamuros. Antonio Alonso is a privileged witness to criminal history and forensic medicine in Spain. A forensic geneticist, he directed between 2019 and 2024 the National Institute of Toxicology and Forensic Sciences. Retired, he now recounts in the book La huella invisible (Crítica) how DNA has changed the history of justice in Spain.