Depression. Psychosis. Stress. Feelings of being overwhelmed.
These are just some of the factors that drive women to kill their children.
Such crimes evoke horror and clash with traditional notions of women as natural, nurturing caregivers. But these killings are neither a new nor a rare phenomenon, experts said.
More than 200 women kill their children in the United States each year, according to the American Anthropological Association.
"For all the anxieties we have about stranger abductions, for young children, parents are far more lethal," said David Finkelhor, director of the Crimes Against Children Research Center at the University of New Hampshire.
Authorities said Shaquan Duley of Orangeburg suffocated her two toddlers and left their bodies inside a car in the Edisto River. Orangeburg County Sheriff Larry Williams said Tuesday the responsibility of being a mother "was a bit much for her."
The case immediately drew comparisons to that of Susan Smith of Union, who is serving a life sentence for drowning her two sons in 1994. But a host of similar cases can be found. Take Andrea Yates of Texas, who drowned her five children in a bathtub in 2001. Or consider Ellen Feinberg, who stabbed her two sons, one fatally, in Illinois in 2002.
Harold Morgan, a forensic psychiatrist who teaches at the University of South Carolina, has examined a half-dozen women who killed their children and thinks most fall into four broad and, at times, overlapping categories.
Some are psychotic or out of touch with reality, such as a Lowcountry woman who threw her baby in a river in the 1980s because she thought the infant was possessed by the devil or a demon, Morgan said.
Others are narcissistic, self-centered and feel entitled to do whatever they want, he said.
A third group includes women who are depressed and want to spare their children the suffering they endured in life, Morgan said.
Another group includes needy, insecure mothers who feel overwhelmed by their circumstances. "The only way they can see to fix their problems is to get rid of their children," he said.
Libby Ralston, executive director of the Dee Norton Lowcountry Children's Center, said she seldom sees cases where children are killed simply out of malice.
"I think parents sometimes just get stressed to the point where they feel totally trapped and inadequate in being able to meet their kids' needs and they don't see any other options," she said.
About 1,500 children die on average each year at the hands of a parent or caregiver, with rage or out-of-control discipline often a factor, Finkelhor said.
In South Carolina alone, 231 children have been slain by their parents since 1993, according to the State Law Enforcement Division.
Fathers have been charged with their share of killings as well. Just last month, a Summerville man was charged with allowing his 2-year-old son to die from unspecified injuries and then hiding the body in cement.
Experts said there are a variety of places parents can turn to for help if they find themselves overwhelmed or unable to care for their children. The state's so-called Daniel's Law allows an infant less than 30 days old to be left at a hospital, police station, fire station, outpatient medical facility or any place of worship, as long as the child is left in an employee's hands. Parents also can seek help and advice through hot lines, churches and social service agencies.
Ralston urged people who suspect child abuse, neglect or the potential for harm to contact authorities immediately. "It may save the life of a child."