Marchena was born in
Las Palmas. He studied in General Alonso High School of
Laayoune, in the
Spanish Sahara and in the San Ignacio de Loyola School of Las Palmas. He graduated in Law from the
University of Deusto,
Bilbao, in 1981, obtaining the highest score in the degree exam (with Honors). He received his doctorate in Law from the
University of La Laguna in 1991, also obtaining the highest score,
cum laude. He developed most of his judicial career in the Provincial Court of Las Palmas, the High Court of Justice of Madrid and the Supreme Court. He has also been prosecutor, working in the Technical Secretariat of the
Attorney General's Office and in the Prosecution Office of the Supreme Court. In addition, he has been Associated Professor of Law in the
University of Las Palmas, in the
Autonomous University of Madrid and in the CUNEF University of Madrid. In 23 March 2007 he was appointed magistrate of the
Supreme Court and in 27 October 2014 he was appointed Chair of the Criminal Chamber of the Court. On 11 November 2018, it was rumored that he would be proposed as the next
President of the Supreme Court and of the General Council of the Judiciary. On 20 November, he announced that would not present his candidacy to chair the Court. In 2019, he was the head of the seven-member criminal court that
judged the actions of the
Catalan separatist leaders. He is in possession of the distinguished Grand Cross of the
Order of St. Raymond of Peñafort, granted by Order of 24 June 2002 and he is not registered in any association of jurists. ==Awards==