Hensley was held captive for 11 days during a 1993 prison riot. The riot resulted in the murders of a guard and nine inmates and a siege by 2,000 correctional officers, State troopers, and National Guard personnel. Between 1988 and 1994, assaults on employees in State and Federal correctional institutions increased from 1,695 per year to 13,379. During the same period, the prison population increased by 60 percent. Factors that have changed inmate attitudes have included longer sentences, restrictions on parole, and increasingly severe conditions of confinement. At any one time, as many as one-third of Lucasville's 1,050 inmates are locked down for 23 hours per day. Critics of such facilities argue that such conditions have destroyed the traditional tacit agreement between correctional personnel and inmates, under which inmates avoid behavior problems if they are not treated too harshly.