After passing the Second State Examination in 1966, Jentsch received his doctorate in Marburg with a thesis titled Die Beurteilung summarischer Exekutionen durch das Völkerrecht.
After the 1985 Hessian municipal elections, he was prematurely recalled from office by the city council due to a change in majority.
From June 18, 1991, to February 11, 1992, his portfolio bore the name "Thuringian Ministry of Justice, Federal and European Affairs."
[7] In the headscarf ruling, Jentsch was a member of the minority and, together with Judges Udo Di Fabio and Rudolf Mellinghoff, voted against the teacher's constitutional complaint and thus in favor of the Higher Education Authority of Baden-Württemberg, based on the principle of the neutrality of schools and the headscarf as a political symbol.
In the decision of the Federal Constitutional Court of August 25, 2005, on the dissolution of the 15th German Bundestag, he was the only judge not to take the view of the Senate majority.
[9] The Prime Minister of Hesse, Volker Bouffier, awarded Hans-Joachim Jentsch the Wilhelm Leuschner Medal for services to German unity on November 5, 2010.