LOUISVILLE, Ky. — A sobbing mother was sentenced Thursday to 25 years in prison for setting fire to her home and killing two of her children at Fort Campbell, in what prosecutors described as a scheme to escape a rocky marriage and collect on her soldier husband’s life insurance policy.

In a tearful plea for leniency, 39-year-old Billi Jo Smallwood showed photo albums and her son’s toy chest while professing her innocence to a crime that could have put her in prison for the rest of her life.