hi! additional contributions are welcome, but FYI there have been several questions about trial by combat (not to mention several others on dueling in general), so get started on these:
Was Trial By Combat an actual thing in Medieval Europe? If so, how did really work and how was it regarded?
Was trial by combat ever a "thing"
How common was trial by combat throughout history? How was it conducted?
Did the right to a trial by combat essentially mean extremely talented fighters were able to commit crimes with impunity?
Weapons in a trial by combat/duel
What is the historical significance of the last legal trial by combat in France?
In what circumstances would guilt be determined by trial by combat rather than a jury?