In a moment worthy of the opening scene of Sunset Boulevard, no sooner do we meet Captain Brierly than we find out he's already dead. What the heck happened?
He jumped overboard at sea barely a week after the end of the inquiry [...] as though on that exact spot in the midst of waters he had suddenly perceived the gates of the other world flung open wide for his reception. (6.4)
The Brierly we meet, who is serving as a judge at Jim's trial, seems to have it all: a nice job, respect, a healthy ego. Yet he kills himself at the young age of thirty-two. Something went wrong, but we're not sure what.
Marlow isn't sure either, and he wants to figure it out. But instead of going straight back to the beginning, Marlow goes backwards in stages, Memento style. So after hearing that Brierly is dead, we get additional details through Marlow's conversations with Captain B. This moment, in particular, sheds some light on Brierly's inner turmoil:
"Such an affair destroys one's confidence. A man may go pretty near through his whole sea-life without any call to show a stiff upper lip. But when the call comes [...]"
He broke off, and in a changed tone, "I'll give you two hundred rupees now, Marlow, and you just talk to that chap. Confound him!" (6.14-5)
Something stops Brierly from continuing his thought in his conversation with Marlow – some insecurity we don't know about. Brierly is a pompous, arrogant guy, sure, but he is also apparently subject to extreme self-doubt. Could it be that something about Jim's case sends him down a shame spiral? Did something call attention to his own insecurities?
In the end, Brierly's tragic suicide reminds us of two things:
First, Jim's behavior has consequences for the whole community. Its impact extends far beyond Jim's reputation.
Second, Jim is, unfortunately, not as unique as everyone would like to think. We can't help but wonder if Brierly, like Marlow, wonders if he doesn't have a bit of Jim's cowardice in himself. Could that worry be what sends him overboard?