how does gene fail finny during the"trial"?

Just as Gene tries to deny responsibility for the accident, Finny tries his best to cover up his friend's guilt. They work together to try and thwart the charges that Brinker puts before them, and fully illustrate their very different natures. Gene is being more selfish in his attempts to cover things up, with his lies meant to hide his involvement; Finny is trying only to shield his friend from any implications, and tries to divert attention away from Gene's guilt. But this is one time that they cannot deny what has happened, and the truth comes out, despite their wishes that it be their secret. This is a unique occasion, because Finny cries, for the first time that Gene has been witness to, and for the first time in the book. He surrenders his will to fight, which may be partly to blame for his accident at the end of this chapter.