(JTA) — Two well-known Polish Holocaust historians are on trial for alleged defamation over their claim that late mayor of a town near Warsaw who saved one Jewish woman was involved in the murder of 22 other Jews.

Jan Grabowski and Barbara Engelking were sued last year in civil court by a niece of the mayor for what they wrote about him on their 2018 book “Night Without an End,” about Polish collaboration. Their trial opened on Jan. 12, the OKO news site reported Saturday.

The late mayor, Edward Malinowski, was acquitted in a trial after World War II of collaborating with Nazis in the town of Malinowo, which he headed and which is located about 70 miles northwest of Warsaw.

During the trial, the issue of the 22 murdered Jews arose. But a Jewish woman he saved, allegedly in exchange for payment, Estera Siemiatycka, testified in favor of the mayor, and he was acquitted.

In their book, Grabowski and Engelking revisit those charges, writing that in 1944, “It was said in the village that a group of 22 Jews was hiding in a nearby forest, had been betrayed by Poles and murdered by the Germans. It was said that the mayor of Malinowski was involved in this.“

Asked by OKO whether it was certain that the mayor was involved in the murders, Engelking said it was not certain. “I didn’t write that I thought he had betrayed the Jews. I reported on the witness’s opinion,” she said.

Engelking added:  “I think that despite the fact that she [Siemiatycka] had a bad opinion of him [Malinowski], she wanted to do him a favor and show her gratitude for saving her life.”

In subsequent testimonies, Siemiatycka said the person responsible for betraying 22 local Jews to the Nazis was a gamekeeper from a nearby village, who was killed, reportedly by partisans, TVP reported. Her testimony was corroborated by several witnesses, including Jewish ones, the news organization also reported.

In 2019, the Polish parliament passed a law that makes it illegal for to blame the Polish nation for Nazi crimes and exposes those who do to civil lawsuits. Critics of this law, including the Yad Vashem museum in Israel, said it risks stifling historic research into World War II in Poland.

Malinowski’s niece, Filomena Leszczyńska, filed suit under the new law. She is demanding compensation of about $26,000. A ruling is expected next month.