Two mishnayot! First - a description of how the Sanhedrin sat -- in a semi-circle, so the judges could see each other. Scribes transcribed the arguments. Plus, the hierarchy of the seating, and how the judges would rise through the ranks. Plus, the way the Jewish people would not broach the borders of sin, even when that border is relatively passable, such as hedge of roses. Which is understood as sufficient barrier to sin for a husband and wife, when the laws of taharat hamishpachah (niddah) require them to separate. With a note for Jews as people who are not too likely sin. Second - the court intimidates the witnesses to make sure they are sufficiently serious about the weight of what they have to say, in several different scary ways. And then the mishnah takes a side-step to interpret the verse of Kayin killing Hevel (Cain and Abel), and how serious that was. Plus, how man (Adam) was created alone - which attests to the value of one person, who is, indeed, an entire world. Which is, of course, another indication of how serious one's testimony is. Plus, an argument for both peace among people, and also, monotheism, as it turns out. And exactly why people should bother themselves to come forward to testify, even in light of the intimidation of witnesses in a capital case.