Why does Jem say, "We've got him" at the end of the chapter? What does he mean by this? Chapter 17

Jem really feels that Atticus's cross examination of Bob Ewell proved without a doubt that Ewell is a liar and responsible for his daughter's bruises.

jem feels that his father is doing his best as he can and that mayella is lying becasue she scared that her dad might do something else to her if she told on him i wouldnt care i would have told anyways...

i hate when people lie on other people this book made me sooooo mad

hi