When the Japanese occupied Southeast Asia during World War II, there were soldiers who committed war crimes. Convicting those people of crimes was an extremely complex process.
There are a lot of materials pertaining to this process in the Australian National Archives. In looking through them, I still haven’t figured out exactly how the entire process worked, but I can see what the major problem was.
When the war ended, the Allies brought their soldiers who had been prisoners of war (POW) home, and they arrested Japanese soldiers (some of whom were Korean and Taiwanese) more or less wherever they could.
This then created a problem, because in order to convict Japanese Prisoner T1121 who was being held in a Bangkok jail, one had to get evidence from former POWs that he had in fact committed a criminal act and that they had personally seen it.
However, those people had all gone to their homes in Australia, the UK, America, etc., and therefore all had to be found first.
What made things even more difficult is that the POWs didn’t know the names of many of the Japanese who had committed crimes. Instead, they had given them their own names, like “Mad Mongrel,” “Tiger,” “the Screamer,” “the Silent Basher,” “Puss in Boots,” “Silver Bullet,” “Doctor Death,” and “Mussolini.”
So the investigators had a difficult task. They had to figure out where the Japanese soldier had worked, which former POWs had been in that camp, and then they had to locate those people and send them pictures of Japanese soldiers in custody and ask them if they could identify them.
You find a lot of cases where people couldn’t identify someone, or they could identify the person but had not seen him do anything. At other times they suggested that the pictures be sent to someone else who they thought might be able to identify the person.
Then of course there were Japanese soldiers who were identified. When this happened the former POWs wrote sworn affidavits in which they stated what they had seen the person do. Those affidavits were then used in trials.
[The pictures here are from NAA: D844, 167/1/12 PART 1, War crimes – Japanese (Brenkassi Burma/Siam railway, Kawasaki Kobe house, Hakodate, Fukuoka, Hintok, Hindato, Kalidjati ), 1946-1948, pages 221, 223, 225 and 227.]