According to court documents from his Dutch trial after the Second World War, he indicated that his name is written with an umlaut.

Kotalla was born in Upper Silesia, then German territory that was assigned to Poland after World War I.

After his return from the hospital in Kamp Amersfoort he was called "UnterSchutzhaftlagerführer", in which position he replaced Berg as commander in his absence.

In the course of 1944, Kotalla started a relationship with 21-year-old Louisa Johanna (Loes) van den Bogert, a Dutch typist who worked at Abteilung III of the camp.

Kotalla was known, among other things, for his brutality during the daily roll call, kicking and hitting prisoners with a club.

The Special Council of Cassation had Kotalla undergo a psychiatric examination by a neurologist, who concluded on 4 October 1949 that he was "not diminished" while committing his crimes and that "his nervous disposition cannot excuse the many ill-treatments he committeded, since they too clearly exhibit a systematic character.” Partly on the basis of this conclusion, the death penalty was maintained on 5 December 1949.

At the request of his lawyer, a second psychiatric examination was conducted which concluded in a report dated 18 March 1950: that he was indeed diminished.

[7] The report stated: "Where a compulsive neurotic character is still complicated by an organic brain lesion, it is often the case that patients still have sufficient insight into the illegality of certain behaviors.

It is for this reason that we believe that Joseph Kotälla, while committing the offenses charged against him, suffered from some disturbances of his mental faculties such that these facts, if proved, will generally be imputed to him in a diminished degree.

"[8] On 5 December 1951, based on the latest psychiatric report, Kotalla's death sentence was commuted to life imprisonment by royal decree.