Clarence Darrow has to somehow play a role in the conclusion of the show the two references from Howard and Walt name dropping him in BB, I just searched him up on Twitter and came across this thread that explains it incredibly well.
And just to opine a bit on Howard, I wonder to what extent he idolized Darrow or found interest in that case due to any early idealism/different goals in life, as he mentioned to Kim in season two.
If a lot of Howard's character arc was centered around his lack of agency and his end in being at the wrong place at the wrong time and Clarence Darrow's famous speech ultimately amounting life to luck and conditioning, not conscious choice- that connects back to the idea of Jimmy being incapable of change and inherently the way he is and the question of if he can even still be different despite everything- as Howard saw in him initially and Chuck never believed.
Just want to quote a little from Darrow's Wikipedia page, some of which that reminds me of Howard's monologue.
"The Leopold and Loeb case raised, in a well-publicized trial, Darrow's lifelong contention that psychological, physical, and environmental influences—not a conscious choice between right and wrong—control human behavior. Darrow's psychiatric expert witnesses testified that both boys "were decidedly deficient in emotion". Darrow later argued that emotion is necessary for the decisions that people make. When someone tries to go against a certain law or custom that is forbidden, he wrote, he should feel a sense of revulsion. As neither Leopold nor Loeb had a working emotional system, they did not feel revolted."
Honestly this makes the common prediction that I've even held of Jimmy spending his days in prison and doing good/rehabilitating inside even more of a possibility; I'm a prison abolitionist or at least close to being one though, so I'm sympathetic to the idea of reformation on the outside but consequences come in line with the overarching morality of the universe and I find prison more fitting for Jimmy.
Anyways these are just brief thoughts- I need to think on it more and all the themes it could link to and specific relevance to Howard, Jimmy, Chuck, and Kim's characters.