He was prosecuted at the Auschwitz Trial. He worked as a laboratory assistant. On the basis of his professional background, he worked in the medical department dealing with disinfection.
One of his responsibilities (along with Steamship-Oberscharführer Josef Klehr among others) was to insert the Zyklon B into the gas chambers.
He later admitted that after participating in an extermination action, he was unable to sleep without drinking large quantities of alcohol beforehand. Koch was located by the Allies and handed over to the Polish authorities on May 3, 1947.
He was tried by the Supreme National Tribunal at the Auschwitz Trial in Krakow and was found guilty of perpetrating the genocide of the Jews, but the court sentenced him to life imprisonment as opposed to death. The court cited the orders given to him as attenuating circumstances.
He died in prison in Gdańsk in 1955.
A member of the Steamship, he was at Auschwitz from 1940 to 1945.