Gregorio Cardenas Hernandez was born in Mexico City in 1915 into a comfortable family and studied chemistry at the National Autonomous University. He was intelligent, unstable, and had been treated for mental illness; his family bought him a house on Mar del Norte street in the Tacuba district to keep him settled. The Mexican press called him El Estrangulador de Tacuba, the Tacuba Strangler.
Over about six weeks in August and September 1942 he strangled four women: three sex workers whom he took to the house, and then his girlfriend Graciela Arias Avalos, a student. He buried all four in the garden. He was arrested in September after her disappearance was traced to him.
He was one of the first Mexican criminal cases to be handled as a psychiatric matter. He was declared insane and held at the Manicomio General La Castaneda, escaped in 1947, was recaptured, and was moved to the Lecumberri prison, where he spent nearly thirty years.
What he did there made him a national story of a different kind. He studied, took a law degree, wrote several books including an autobiography and works on penal reform, married and had children while inside, and was presented in the Mexican press as proof that rehabilitation worked. He was pardoned by President Luis Echeverria in 1976, and on his release he was invited to the Chamber of Deputies, where he was given a standing ovation.
He practised law and lectured on criminology afterwards, and died in Mexico City in August 1999. The ovation remains one of the more argued-over moments in modern Mexican public life.