French historian Henri Locard on Tuesday accused defense lawyers at the Khmer Rouge tribunal of subjecting him to “cold torture” during his time on the stand, and later branded their behavior as “criminal.”

Testifying for a final day, Mr. Locard lambasted Anta Guisse, a lawyer for Khmer Rouge head of state Khieu Samphan—who is on trial alongside the regime’s second-in-command, Nuon Chea—for her efforts to discredit his expertise on Monday.

“I didn’t sleep very well this night, so it might be difficult for me to answer you because yesterday you practiced cold torture on me and now I know what cold torture means. I wasn’t able to sleep between 1 and 4 in the morning,” Mr. Locard said.

The 77-year-old historian then appeared to compare his treatment at the tribunal to that of Cambodians who returned from abroad during the Pol Pot era.

“When people would return from abroad, the idea was to gift one’s persona to Angkar. So, if you want to continue with cold torture, after three days maybe I will gift my persona to Angkar as well,” he said.

Ms. Guisse replied that she was simply doing her job. ...