On 9 August 1946, Josef Mueller was arrested in Dortmund and charged with having murdered Ernst Thälmann on the night of 18 August 1944. Thälmann had been leader of the Communist Party of Germany (KPD) and was killed in Buchenwald concentration camp. 

Mueller had been in Buchenwald as a criminal and “worked” in the crematorium. He admitted that he had killed political prisoners with a club and then incinerated the corpses. Regarding Thälmann, he stated that he had only heard gunshots and that the corpse was later brought to him to be burnt.

The testimony of the witnesses contradicted this version of events: some insisted that Mueller had killed Telman the usual way – with a club - whereas others insisted that they had seen the moment the shot was fired. Mueller received cigarettes, extra food and vodka from the guards for the murders (it appears that Mueller had much blood on his hands). He was arrested in the half-burnt villa in which he was hiding.

However, Mueller was not among the 31 defendants at the special Buchenwald Trial. The main defendants at the trial were Josias, Hereditary Prince of Waldeck und Pyrmont (Himmler's representative who acted as "judge" at Buchenwald camp), Hans Schmidt (Chief of Staff to the camp commandant) and Wolfgang Otto (SS-Stabsscharführer, a member of the Execution Team).

On 21 April 1946, the court heard witness statements about the murder of Thälmann. Marian Zgoda, a Czech, said that the SS had personally sent and burnt Thälmann’s body in the furnace: “It was obvious from the colour of the ashes that the body had been burnt along with all the clothes, the ashes were a darker colour, whereas normally they are almost white.” 

It was decided that Ernst Thälmann should be killed at Hitler’s headquarters, the "Wolf's Lair",  shortly after the failed assassination attempt on Hitler on 20 July 1944. After his conversation with Hitler, Heinrich Himmler made a mark opposite Thälmann’s name (paragraph 12 of the conversation plan) which simply read: “Execute”.

Marian Zgoda was among those who claimed that Thälmann had been shot - at the time the witness was allegedly hiding behind a mountain of slag: “I could only see from behind. When the prisoner passed the chain of four SS men and entered the corridor of the crematorium, he was followed by three gunshots. The SS men standing outside and two civilians entered the crematorium and closed the door behind them. About three minutes later a fourth shot was fired, apparently just to make sure.” 

On 14 September 1944, the German news agency DNB announced that Thälmann had died in an Allied bombing attack on Buchenwald on 23 August.

The fate of the immediate perpetrators of the murder was undeservedly good. Wolfgang Otto, for example, ended up as a teacher in a Catholic school. Josef Mueller went on to be convicted by a different court and was released in 1957.

The Hamburg-based Zeit newspaper wrote: "Anyone who reads the court documents cannot escape the impression that all the efforts of the prosecutors over 20 years have been aimed only at obtaining evidence of the impossibility of punishing these crimes...”

Source:

The newspaper “Pravda”, No. 189 (10271) from 10 August 1946