| Quote #4
"It was an elbow. The Gilbert's dog found it." (2.70)
We don't know exactly how they knew this was Susie's elbow, or what shape it was in when they found it. It comes to symbolize Susie's death and to stand in for the rest of her bones, which are never found.
| Quote #5
But when they held up the evidence bag with my hat in it, something broke in her. The fine wall of leaden crystal that had protected her heart […] shattered. (2.115)
For some reason, the saliva-covered hat, which Mr. Harvey uses to gag Susie, is what convinces Abigail that Susie is dead. Why is this more convincing to Abigail than the elbow? Well, because she recognizes it. She made it. It's a psychological thing.
| Quote #6
"All evidence points to your daughter's death. I'm very sorry." (2.131)
Some of the worst words a parent can hear.