Deep inside a hushed fortress at the edge of the Colorado Rockies, behind razor-wire coils and reinforced steel doors, one of America's most feared inmates was being carefully watched.
There was little that T.D. "The Hulk" Bingham could do that escaped the attention of intelligence agents at the Supermax federal prison, the nation's tightest lockup.
They feared that Bingham, believed to be one of the walrus-mustached warlords of the Aryan Brotherhood prison gang, might launch his soldiers into a bloody race war. They monitored his visitors, tapped his phone calls, studied his mail.
But in August 1997, an alleged order slipped out of Bingham's cell in "the Alcatraz of the Rockies," sneaked past impregnable walls and gun towers, foiled a network of cameras and surveillance lasers, and unleashed carnage at another high-security compound 1,700 miles away. At the federal prison in Lewisburg, Pa., Brotherhood members armed themselves with shivs and charged black inmates, slaying two.
Against high-tech scrutiny, prosecutors say, Bingham had employed a decidedly low-tech method, one used by spies in George Washington's Revolutionary Army but which dates to the first century, when the Roman writer Pliny the Elder recorded its use: invisible ink. Prisoners make it from urine or citrus juice.
The Aryan Brotherhood's arsenal of cloaked communication is central to the trial underway at U.S. District Court in Santa Ana, which started in March and is the first of several murder and racketeering trials targeting the gang's alleged leadership.
To run their barbed-wire empire of terror, drugs and extortion, the government says, Brotherhood bosses improvised methods of smuggling messages while under constant surveillance in some of the tightest cages ever built.
They shouted through the pipes of drained toilets. They wadded up notes and slipped them into mop handles. They possessed an eclectic system of codes and cryptograms, and the gift of time to perfect them.
Federal prosecutors have introduced stacks of coded documents in the current case against alleged kingpins Bingham, Barry "The Baron" Mills and two lesser figures. The evidence includes a gang membership list encoded in a dual-alphabet cipher devised by Sir Francis Bacon and a call to arms embedded in the text of a library book on Napoleon Bonaparte.
The documents are crucial to the government's case because they bolster -- or so prosecutors hope -- the testimony of its witnesses, many of them gang defectors, killers and practiced perjurers whose credibility defense attorneys have attacked.
The evidence also reflects how the gang has evolved, since its founding at San Quentin State Prison in the 1960s, into what prosecutors call a highly organized nationwide syndicate that relied on the quick, effective transmission of orders from its high command.
Still, the defense maintains that what prosecutors view as clear-cut physical evidence is ambiguous at best. Defense lawyers don't deny that the Brotherhood sneaked messages back and forth but insist it was for the same reason that the gang made shanks: for self-defense in an environment where enemies far outnumbered friends.
To fool the Persians, the Spartans hid notes in the bellies of slain rabbits. Genghis Khan commanded armies by pigeon relays. Napoleon crushed enemies with the help of signal towers. The Allies won one of World War II's key battles by cracking the Nazis' Enigma coding machine.
And the government's campaign against what it has called one of the nation's most murderous prison gangs has played out, in part, on the field of cryptology -- as an extended duel between code-makers and code-breakers, between inmates devising ingenious means of smuggling messages and agents charged with thwarting them.
Dip a Q-tip in citrus juice, urine or bleach, write with it, and the resulting words will remain invisible until exposed to direct heat. Despite its ancient pedigree -- and easily available instructions in reference books -- the technique was obscure to Bureau of Prisons experts in 1997, when authorities say Bingham's use of it blindsided them.
"We didn't know that that existed at the time," said Danine Adams, a prison agent who monitored the gang's correspondence at the Supermax. She said it was likely that Bingham's letter allegedly greenlighting the Lewisburg attacks passed right under a prison agent's eyes.
From the prison in the Rockies, prosecutors say, the letter went to Ron Slocum, a Brotherhood courier on the streets, who in turn sent it to Al Benton, the gang's boss at the federal prison in Lewisburg.
Benton testified that he received the letter, which carried an innocuous text in regular ink to mask its secret message, in the 4 p.m. mail Aug. 27. He and an underling heated it over a match flame, which brought the hidden writing into view:
"War with DC blacks, T.D."