What was the reason given for bringing in Bessie’s body?

The deputy coroner points out that the “circumstances” of the trial, forces him to bring Bessie's body into the courtroom. The display of her mutilated body shocks the court. More importantly, it shocks bigger. For the first time, Bigger sees what he has done to somebody that loved him. The effect of bringing the body in puts Bigger and his crimes into more perspective. The ashes of Mary did not have the same effect.