והיא יושבת תחת תמר דבורה ... (שפטים ד-ה)
The Haftorah details “Shiras Devorah” - the Shirah sung by Klal Yisroel in the aftermath of battle between the Jewish Nation (led by Barak ben Avinoam and the tribes of Naftali and Zevulin) and the army of the Canaanite General, Sisera.
The Navi tells us that Devorah HaNeviah, “Sat under the ‘Palm of Devorah’ [a palm tree]” so that she would not violate the Halachos of Yichud when men would consult with her. In fact, the word "תמר" is the same numerical value (640) as the words "צנועה היתה" - “she was modest.”
However, as we know, in every Halachic dispute there must be two men present, the accuser and the accused, essentially two potential witnesses to dispel any suspicion of wrongdoing on the part of Devorah HaNeviah when they came before her. Why then was she required to sit under the palm tree in plain view of the public?
The Chida, Chacham Chaim Yosef Dovid Azulai zt”l answers that Chazal (Avos 1:8) surprisingly say that when the two plaintiffs are in front of a dayan, the judge is required to regard them both as guilty until proven innocent, but when they leave they should both be assumed innocent unless proven otherwise. This ensures a more impartial judgment.
Thus, as the Gemara (Kiddushin 80b) states, since two suspected “guilty” people are considered immoral, they cannot serve as kosher witnesses with regard to the issue of Yichud, and Devorah needed to sit under the palm tree in public so that she would be above suspicion.