Spencer Tracy played his version of Darrow as a firebrand in court, and a bit of almost a jovial character out of court. That's actually very different from Welles approach who instead goes about depicting his Darrow quite a bit differently. The various long fights of his career as well as his age can be seen through Welles is own face as he expresses the wear of this sort of life through his own performance. In the few moments we get of Wilk outside of the courtroom or engaged in some other court related proceedings Welles frankly depicts a more realistic sort of man who carries a certain somberness as a man who perhaps has a few hesitations and reservations regarding his duty as normal man would. Welles presents a man who frankly does not have the energy or time to be a character outside of the court, because that life requires so much of him. Of course the majority of Wilk's screen time is devoted to defending the two men. This includes several scenes proceeding the actual trial where Wilk attempts to save the men early by trying to have them both be proven to be insane, this proves difficult though since both men have already confessed to the crimes as well as have been proven to be sane by the prosecutor's own doctors.
This leaves Wilk to basically only use his own considerable talent to try to save them from hanging. This includes several moments where Wilk points out or indirectly insults the method of his opponents. Tracy again played this method as very loud and overt. Welles is even more incisive in revealing Wilk's intelligence in these scenes though he takes a far more understated approach. Welles instead of outwardly just blasting them with his views, as though he's trying to put them into submission, brings a more persuasive quality as though his corrections are not to make himself feel smarter, but actually promote something better for all. Welles quietly exudes this intelligence in Wilk so well and tears into any given scene so well, without ever raising his voice either. It's quite a different approach for this sort of character, but it works incredibly well to realize actually the beliefs of his character in addition to his methods as a lawyer. The shrewd nature of Wilk can only go so far though, and due to the men's obvious guilt it leaves him no alternative to plead guilty in order to directly appeal to the judge for mercy for the men.
Wilk's summation is a particularly long one but Welles is riveting for every moment of it. Again Welles actually stays fairly withdrawn but shows what Wilk is driving it as he's attempting to appeal to humanity itself. There is no sympathy in his words for the act, but Welles instead gives the passion within Wilk's words that advocate for justice not revenge. There is a powerful emotionality in Welles as he expresses the earnest need in Wilk that love will outweigh hate. Again Welles does so well to be persuasive as Wilk as he conveys the way Wilk is most disturbed by the insistence that more blood should be shed, and Welles wonderfully illustrates this philosophy through his sober performance. As Welles is able to bridge a gap from any political statement to instead making the words from Wilk feel only as truths. The scene could have been a long monologue of statements. Welles though brings such a weight to each word and manages to make it absolutely convincing that the men's lives would be spared. As great as that scene is though my favorite moment of his performance is brief one after the men have been sentenced to life in prison and seem to be ready to continue in their pompous "superior" ways. Wilk finally no longer has to defend them, and is able to take them to task. Welles is outstanding as he once again takes that incisiveness in his performance to Wilk's disgust as he breaks down their own foolish philosophy showing just how little regard he had for either man. This is terrific work from Welles as he manages to find quite the unorthodox yet such an effective approach to this sort of role.