Jessica Morris is a character in Season Six of DEXTER. She was a prostitute, whose death is the result of a heroin overdose. However, there is evidence to support she may have been the victim of involuntary manslaughter due to one other person being present at the scene.
It is later revealed that it was Thomas Matthews who was present during her death, and attempted to perform CPR to revive her. He however didn't know that she had overdosed and just cracked her ribs causing more blood to flow out. However, when he realized she had overdosed, he stopped, and left the premises.