Cristian Fernandez "acted with premeditation" when he smashed his helpless brother David Galarrigo so badly that he fractured his skull causing a bleeding brain and bruising to his left eye.
He died two days after the vicious attack at his family home in Jacksonville, FL.
Assistant State Attorney Mark Caliel told said the boy acted with premeditation when he beat the toddler on March 14.
He said: "The brutal beating death of a 2-year-old is one of the factors that we must consider."
