Two South Carolina women will spend the rest of their lives in prison for beating a toddler to death in 2009, a sentence that fits their crime, the case's prosecutor said on Friday.Erika Mae Butts and Shanita Latrice Cunningham, both 25, each received a life sentence from a Charleston judge on Thursday, two years to the day after 3-year-old Serenity Richardson died while in their care. They pleaded guilty to the crime in August. "It is nearly impossible for words to accurately describe what these women did to that poor little girl," said Elizabeth Gordon, assistant managing solicitor for Charleston County. "They beat her repeatedly both with a belt and with plastic coat hangers. You can see the outlines of the strikes on this child's body. There is not one area of this child's body that was unharmed except for the soles of her feet." Serenity was visiting Butts, her godmother and her mother's best friend, and Cunningham, who was Butts's lover, for two weeks at their home in Summerville, South Carolina when the abuse took place, Gordon said. Serenity's mother, Ieshia Richardson, lives in Detroit. "The explanation they gave (for the beatings) was that Serenity had a potty accident," Gordon said. "Their explanation is 'we didn't know what we did would kill her.'" "They knew what they did was wrong," Gordon said. When Serenity became unresponsive on November 3, 2009, "they put bleach under her nose and they put ice on her to try to revive her," Gordon said. Butts called her own mother, who called 911. When medics arrived, the child had been dead for some time, Gordon said. She said that in four years of prosecuting crimes against special victims, this was the worst case she had seen. "In most of the homicide-by-child-abuse cases, somebody made a bad decision one day. (Butts and Cunningham) made a decision every single day that they were going to beat that child." An estimated 1,770 children died from abuse or neglect in 2009, according to the Child Welfare Information Gateway at the U.S. Department of Health and Human Services. Most researchers believe the number of child abuse deaths is under-reported, according to the department. The most frequent victims are children ages 4 and younger.