U.S. military spokesmen have said the death was an "apparent suicide." The ACLU said it was the fourth death in custody at Guantanamo in the past year.
"Further deaths at Guantanamo should not surprise us when prisoners are afforded a second class system of justice, are held indefinitely without charge and are given only limited access to their lawyers," said ACLU Executive Director Anthony D. Romero. "Guantanamo Bay has operated for far too long under a shroud of secrecy. The global community and the American public have rightfully lost their trust in the U.S. government after countless reports of abuses and injustices at Guantanamo."
"Guantanamo remains a legal black hole," Romero said. "This is inconsistent with American values and must stop immediately."
Last week the ACLU announced its support for legislation proposed by Sen. Tom Harkin, D-Iowa, that would put a halt to indefinite detention without charge or due process for detainees who have been in custody for up to five years without being told why they were held.
"The military commission system at Guantanamo Bay delivers only the illusion of justice," said Jameel Jaffer, director of the ACLU's National Security Project. "Most of the prisoners have not been charged at all, and those prisoners who have been charged are being tried under rules that are fundamentally unfair."
Critics of U.S. detainment and security procedures have said they want to bring previous suicides and suicide attempts at Guantanamo under increased public attention.