What does Mr. Henderson say is lacking to wrap up the case?
About three pages into the play, Mr. Henderson (County Attorney) asks the sheriff if he had found anything important, anything that would "point to any motive." The sheriff replies that nothing had been found. At the end of the play, when Mr. Henderson, Hale, and the sheriff are coming downstairs, they still have not found any evidence pointing to a motive. In other words, they have found nothing that would indicate any reason why Mrs. Wright would've had to kill her husband, or any reason why she chose to kill him the way that she did. He says to the sheriff (Peters):
No, Peters, it's all perfectly clear except a reason for doing it. But you know juries when it comes to women. If there was some definite thing. Something to show--something to make a story about--a thing that would connect up with this strange way of doing it--
Henderson and the other two men ignore the "trifling" evidence. The women pay attention to the so called trifling details and they discover the motive. Aside from the fact that Mr. Wright was not a kind husband, they find clues, most notably the remains of a strangled bird. This is fairly sound evidence of a motive. The women conclude that Mr. Wright strangled the bird. The women conclude that strangling Mr. Wright was her retaliation, but they sympathize with her and that's why they hide the evidence.