During the occupation of Greece by the Axis powers (1941 - 1944), Koutsogiorgas joined a resistance group and was arrested by the Italians. Afterwards, he practiced law in Athens and was among the defence lawyers of Andreas Papandreou during the ASPIDA trial.
In 1970, he was arrested by the military Junta. After the restoration of democracy, Koutsogiorgas was elected to the Hellenic Parliament, under the banner of PASOK, and served between 1974 and 1989. He also served as Minister of the Interior, Minister of Public Order, Minister of Justice and Vice President of various Andreas Papandreou governments.
In 1989, Koutsogiorgas became involved, along with other PASOK politicians (Giorgos Petsos, Dimitris Tsovolas and Papandreou himself), in the Koskotas banking/embezzlement scandal. He was held, pending trial, in October 1990 despite objections from his defence team on health grounds. The Koskotas trial commenced on March 11, 1991. On April 11, Koutsogiorgas suffered a stroke during trial deliberations and died on April 18.
An uncompromising person, Koutsogiorgas became controversial in death as he had been in life: some viewed him as a martyr, others as having died in disgrace.