Ame had been locked in the box before for wetting the bed and other offenses, police said.
Sammantha was found guilty in June but the penalty phase lasted a month. The defense claimed that her upbringing was a factor in her role in Ame's death. Sammantha's husband was also charged with Ame's murder and will go on trial later this year, KPNX reported.
Two other family members are in jail for their parts in the girl's death. Judith Deal was sentenced to 10 years for child abuse. Cynthia Stoltzman, Ame's legal guardian, was sentenced to 24 years for child abuse. David Deal was sentenced to 14 years, AZ Central reported.
In addition to the death sentence for murder, Sammantha was also sentenced to an additional 76 years for other charges, but was given credit for 2,000 days she's already spent in custody, AZ Central reported.
Executions have been suspended in Arizona due to the fact that the drugs used for lethal injections are not available, KPNX reported. The last attempt at execution in the state was in 2014, when Joseph Wood was put to death. The execution was expected to take 10 minutes but was drawn out for nearly 2 hours, ABC News reported at the time.