In A Separate Peace by John Knowles, how does Brinker get Gene and Finny to attend the mock trial? Why is Brinker so determined to investigate the incident?
It's not enough for Brinker Hadley to believe Gene broke Finny's leg on purpose; he wants someone to say it is a fact. In chapter 7, Brinker and Gene have a conversation at the beginning of the fall semester. During this conversation, Brinker suggests that Gene is basking in his spacious dorm room because he did not plan to have a roommate after Finny broke his leg. Brinker provokes Gene further by saying that the truth hurts. Gene responds with, "The truth will out" (88). These two go to the Butt Room for a smoke, and Gene admits the truth sarcastically to make the others think their assumptions about his role in the incident are ridiculous. Brinker doesn't forget about finding out the truth, however, so he simply waits until the time is right to do it.
In chapter 11, Gene shares his concerns about Brinker with the following explanation:
I had no idea what Brinker might say or do. Before he had always known and done whatever occurred to him was right. In the world of the Golden Fleece Debating Society and the Underprivileged Local Children subcommittee of the Good Samaritan Confraternity, this had created no problems. But I was afraid of that simple executive directness now (161).
From the above passage, the reader learns that Brinker's personality is that of a debater and a leader. When Brinker thinks he is right, he does something about it. Therefore, if Brinker thinks Gene is responsible for breaking Finny's leg, then he also wants to know for sure that he is right. As a result, Brinker organizes a mock trial to force the truth out. Feeling that Gene and Finny won't go along with his mock trial willingly, he has "three cohorts" escort them out of their dorm room after curfew at 10:05 p.m. Gene says the following about the abduction:
His friends half-lifted us half-roughly, and we were hustled down the stairs. . . They steered us toward the First Building (165).
Based on the characterization of Brinker, and how he kidnaps Finny and Gene from their room after curfew, it can be inferred that Brinker is dying to know the truth about how Finny sustained his injury just to prove to himself and others that his assumptions are correct.
The mock trial occurs in Chapter 11. We are told that Brinker and three of his friends burst into Gene and Finny's room one night and forced them to accompany them. Gene writes that he thought it was a kind of end of year prank at first:
His friends half-lifted us half-roughly, and we were hustled down the stairs. I though tit must be some kind of culminating prank, the senior class leaving Devon with a fourish.
As to why Brinker conducts this trial, he seems to be playing at being an adult - the war has filtered in so much into the consciousness of the boys that they feel they need to "play" at being at war too, doing the things that soldiers do in times of war. Note Brinker's explanation that he gives:
"After all," Brinker continued, "there is a war on. Here's one soldier our side has already lost. We've got to find out what happened."
Therefore Brinker, who we already know suspected Gene of knocking Finny off the tree, seems to have appointed himself as the judge in this mock trial, which reflects how much the awareness of war has permeated the world of the boys.