Three suicides at the U.S. detention facility at Guantanamo Bay, Cuba, may have been part of a broader plot by detainees who were using confidential lawyer-client papers and envelopes to pass handwritten notes their guards could not intercept, according to documents that government lawyers filed yesterday in federal court. Detainees could apparently hide documents in their cells -- including instructions on how to tie knots and a classified U.S. military memo regarding cell locations of detainees and camp operational matters at Guantanamo -- by keeping the materials in envelopes labeled as lawyer-client communications. Notes that investigators found after the suicides on June 10 were apparently written on the back of notepaper stamped "Attorney Client Privilege," which allowed detainees to communicate secretly without interference, according to government officials.