It wasn't my fault I shot him. Marissa thought.
It's my mother's. She raised me, and she obviously raised a killer, that's her fault.
Fake flashback.
"Marissa Cooper!" Julies voice rang through the house. "Get down here!"
"Yes, mommy?"
"Look at this!" She held the newspaper up to show little 7-year-old Marissa.
"There were two brothers fighting to death and a girl came between them, and she ended up dying. Idiot right? If that were me, I would have shot him, if there were a conveniently placed gun there, and that's what you will do if it happens. You understand me?"
"Yes mommy."
"Good, now get back to polishing your knives I bought you."
End flashback
"And that," Marissa told the judge, "Is why I shot Trey. Because my mother told me to. And you should always do what your mother tells you too."