Prosecution and Principle of Equality
"In addition to the principles laid out in Robinson,* punishing women for their behavior during pregnancy is precluded by the Cruel and Unusual Punishment Clause’s principle of equality. This principle prohibits the selective and arbitrary application of penalties against minority groups.224 The Cruel and Unusual Punishment Clause’s principle of equality is different from that of the Equal Protection Clause because the principle of equality is not premised on the different treatment of a judicially-identified 'suspect class.' Instead, under the Cruel and Unusual Punishment Clause, the principle of equality is concerned with the unequal treatment of minority groups in comparison to more socially accepted groups.
"In punishing drug-addicted women for their behavior during pregnancy, state prosecutors target one of society’s most unpopular groups and single them out for selective and arbitrary punishment."
Lyttle, Tiffany, "Stop The Injustice: A Protest against the Unconstitutional Punishment of Pregnant Drug-Addicted Women," The New York University Journal of Legislation and Public Policy (New York, NY: New York University School of Law, Spring 2006) Volume 9, Number 2, pp. 812-813.