While that finding, issued in October, was aimed at the entire federal prison system, the report said SuperMax failed to monitor at least half of each month's inmate phone calls for the last year checked.
Prosecutors asked for the death sentence for Mills and Bingham, but the jury deadlocked on that part of the case, and so both face automatic sentences next week of life without parole.
Mills already is serving a life sentence on a previous conviction.
Officially known as Administrative Maximum (ADX) in Florence, Colorado, SuperMax is home to convicted terrorists such as Olympic bomber Eric Rudolph, Unabomber Ted Kaczynski and Ramzi Yousef, who led the first World Trade Center attack.
FLORENCE, Colorado (CNN) -- Two California court cases are raising questions about whether prisoners in the nation's toughest prison, SuperMax, are continuing to commit crimes by smuggling coded messages out of the high-security institution.
