From an earlier answer of mine

Trials for collaboration were one of the hot-button issues in European politics postwar, but Jewish collaboration was somewhat unique. Unlike other forms of collaboration, Jews that collaborated with the German authorities or their lieutenants did so in very moderated circumstances like ghettos or various camps. This meant that the collaborators were themselves prisoners of the same system. Collaboration did not erase the stigma of Jewish identity and it was not uncommon for the Prominenten to end up murdered along with their charges. Chaim Rumkowski, the head of the Lodz ghetto, for example died at the hands of the Germans in 1944 when there was no purpose in having a Jewish council for a now liquidated ghetto. For those collaborators that did survive the war, attempts to bring them to justice in the courts was a difficult legal process that fractured around problematic questions about agency and responsibility.

Overall, there were very few prosecutions of Kapos (ward captains in the camps) or other Jewish collaborators. One problem was that many of these individuals did not survive the war or its immediate aftermath. These individuals could easily end up as victims in the highly mercurial nature of camp life. Those that did survive sometimes ended up the victims of extrajudicial justice within the camps after liberation. For those that did survive, their dual status as oppressors/oppressed made prosecutions rare and difficult. Benjamin Murmelstein, the last Jewish council elder of Theresienstadt had his postwar prosecution by the Czechoslovakians fall apart. Murmelstein himself became a controversial figure among survivors as some Theresienstadt Jews claimed he profitted from his collaboration while he argued he did what he did for the survival of the larger community.

Israel did conduct a series of trials of 38 prosecutions of Jewish Kapos between 1951-1964. However, details on these trials are very sketchy as the Israeli courts have sealed their records for 70 years and they have been only opened quite recently. Even though the Israeli law these individuals were prosecuted under, the Nazi and Nazi Collaborators Punishment Law (1950), could have resulted in a death sentence, the sentences for the 15 defendants convicted under this law were relatively mild. Else Tarnek, a female Kapo and block commander at Auschwitz-Birkenau, received a two year sentence in 1951 but since it had been two years since her arrest, she was released the same day. The Israeli judge said of Tarnek:

We must take the circumstances under consideration: the defendant was placed in charge, against her will, of a block of 1000 persecuted women lived. She herself was a persecuted person, just as they were.

Rather than focus on collaboration itself as a crime, the prosecution in these trials instead focused on violent acts committed by the defendant while collaborating. Witnesses the prosecution called to the stand tended to foreground instances of torture and other physical abuse which the prosecution in turn used to argue that the defendants exceeded the norms of a compelled collaboration.

The Israeli judges in the Kapo trials tried to parse out mens rea (mental state) of the defendants and try to determine if the situation they found themselves in the camp was the compelling rationale for their behavior. The appeals process for Kapos and other collaborators tended to lessen sentences and the judges were often at pains to walk a fine line between condemnation of wartime actions and acknowledging that the defendents were compelled towards them. The Kapos and other Jewish "helpers" such as ghetto policemen did not lend themselves well to standard legal prosecutions because they themselves were often victims of a genocidal regime that loaned them a small amount of power to abuse.

Sources

Bazyler, Michael J., and Frank M. Tuerkheimer. Forgotten Trials of the Holocaust. New York: NYU Press, 2014.

Wolf, René. "Judgement in the Grey Zone: the Third Auschwitz (Kapo) Trial in Frankfurt 1968." Journal of Genocide Research 9, no. 4 (2007): 617-635.