What is the significance of the door being broken and the bird cage broken also in "A Jury of Her Peers"?

Both symbolize the motive for the murder of John Wright and the means to freedom for Minnie Wright.  Because John Wright isolated his wife and stifled everything cheerful out of their home (including wringing the neck of her precious bird), Minnie struck back by strangling the life out of him (just as he did literally from the bird and figuratively from her).  Although Minnie is in jail for the death of her husband for the duration of the story, her actions before the story's action begins have set her free emotionally and psychologically.