Shortly after 16-year-old T.W. was booked into Florida's Polk County Jail in February 2012, his three cellmates punched him, whipped him with wet towels, and nearly strangled him with a pillowcase. They then urinated on him, sprayed his face with cleaning fluid, and stripped him naked before wrapping a sheet around his neck, tying the other end around the window bar, and pulling so tight he lost consciousness. They repeated this attack three times over the course of several hours without jail guards on regular rounds even noticing, a federal magistrate judge found.

Around the world, children languish behind bars, sometimes for protracted periods. In many cases, as with T.W., they face brutal and inhumane conditions.

The lack of record-keeping and a wide array of institutions means that the number of children held worldwide in such environments is not known. The United Nations children's fund, UNICEF, has estimated that more than 1 million children are behind bars around the world. Many are held in decrepit, abusive, and demeaning conditions, deprived of education, access to meaningful activities, and regular contact with the outside world.

Many of these children—and adults who were convicted of crimes committed when they were children—have received excessive or disproportionate sentences that violate international law, which requires that imprisonment of children be in “conformity with the law and shall be used only as a measure of last resort and for the shortest appropriate period of time.”

Others are held for acts that should not be crimes at all, such as skipping school, running away from home, having consensual sex, and seeking or having an abortion. Some have never been tried for their alleged crimes; others are tried as if they were adults and, when convicted, sent to serve time in adult prisons.

Migrant children are also routinely held in immigration detention, contrary to international standards. Children with disabilities and others may be institutionalized in the guise of protection.

A UN study expected to be finalized in 2017 promises to put international focus on the detention of children and hopefully result in more systematic monitoring of abusive practices, increased compliance with international standards, and a dramatic reduction in the number of children deprived of their liberty.