Reference for Bava Kamma 70:19

אי מהתם הוה אמינא פטור מדמי חטין וחייב בדמי שעורין קמ"ל דפטור לגמרי

[presents a case where it was] the plaintiff who was certain and the defendant doubtful.<span class="x" onmousemove="('comment',' [How then could R. Hiyya maintain that our Mishnah deals with a case where both were certain in their pleas.] ');">¹⁵</span>

Jastrow