The first judicial trial of the former SS men – members of the SS-Sonderkommando Kulmhof – took place in 1945 at the District Court in Łódź, Poland.

The evidence against the accused, including testimonies by surviving witnesses, former prisoners, and mechanics attending to repair needs of the SS, was examined in Poland by Judge Władysław Bednarz of the Łódź District Court (Sąd Okręgowy w Łodzi).

[2] Three convicted defendants were sentenced to death,[3] including the camp deputy commandant Oberscharführer Walter Piller (wrongly, Filer); the gas van operator Hauptscharführer Hermann Gielow (Gilow), as well as Bruno Israel from Ordnungspolizei (Order Police), his sentence was later commuted to life.

All three were members of the SS Special Detachment Kulmhof responsible for the extermination of Jews and non-Jews during the Holocaust in occupied Poland.

[6][7] After liberation by the Soviet Army, the new government of Poland began its official investigation into the Chełmno war crimes on May 24, 1945.

Truckloads of ashes of its victims were dumped in the Warta river daily, the "palace" was blown up with rubble removed to foundations, mobile gas-chambers and loot were driven back to Berlin, written records were destroyed, including train departure records.

[10] Some of the key evidence was mistakenly discarded in the trash in 1945 (i.e. over 5,000 pairs of damaged shoes from a destroyed synagogue in Koło), or hauled away as usable materials, including wooden fencing and cremation grids; few people were aware of its importance.

[8] By comparison, other former death camps were overflowing with direct evidence of war-crimes, as in the case of the Majdanek trial decided several months before.

The SS Master Sergeant Walter Piller testified about the final phase of the camp operation, including 1944 deportations from Łódź.

[14] The first Chełmno trial in Poland established many critical details from the camp history, but also revealed the operation of mobile gas chambers, which used exhaust fumes as the killing agent, diverted into sheet metal-lined vans.

[14][15] Judge Władysław Bednarz, assisted by the Deputy Recording Clerk, heard testimonies of key witnesses including Szymon (Simon) Srebrnik (age fifteen), who survived being shot in the head during the Germans' last execution of Jews at the camp, and Michał (Mordechaï) Podchlebnik, who escaped in 1942 into the surrounding forest from the burial Sonderkommando.

He was at the camp for 10 days digging mass graves in January 1942 at the time of the Nazi Aktion Reinhard.

In Grabów I met Winer...The second survivor from the Jewish Sonderkommando, Szymon Srebrnik, was from Łódź and 15 years old at the end of the war.

Srebnik worked at the forest camp during the second extermination phase, when the bodies were cremated after being delivered in the gas-vans.

He was accused of committing crimes against the Polish nation under the PKWN Decree of August 31, 1944 pertaining to Nazi War Criminals (the so-called Sierpniówka.

[3] The very Decree of August 31, 1944 used in their sentencing was amended in December 1946, making the laws not applicable from the outset, in connection with the Soviet World War II crimes in Poland.

The first camp commandant, SS Sturmbannführer Herbert Lange, was killed in action on April 20, 1945, near Berlin.

The second head of Chełmno, Hauptsturmführer Hans Bothmann who made substantial improvements to the killing method in the final phase of the camp operation, committed suicide in British custody in April 1946.

The men were then transferred to Chełmno after being selected by Herbert Lange[25] Fifty-six years after the end of World War II, he was convicted as an accessory to murder.

Mania was found guilty of helping to load prisoners into gas-vans and collecting their watches and jewellery, which he also stole for himself.