Alberto Sierra to soon learn fate as closing arguments in death penalty trial get underway

Closing arguments are underway in the death penalty trial of Alberto Sierra, the man who pleaded guilty to killing his estranged wife and her two young daughters more than a decade ago.Sierra, 42, has admitted to authorities that he killed his estranged wife, 29-year-old Gladys Machado, and her two daughters, 6-year-old Julia Padrino and 3-year-old Daniela Padrino, by suffocating all three with a plastic bag in 2012.During closing arguments inside a Miami courtroom on Monday, Sierra sat in silence as the jury saw photos of the victims one last time, and as the prosecution showed a small mannequin roughly the size of Daniela explaining how the crimes were calculated and heinous."He knew that everyone in that house had to die," prosecutor Abbe Rifkin said. "Those children knew him. They were verbal. They would tell."The defense has argued that Sierra suffered permanent brain damage when he was hit by a car as a child.