PRISON POPULATION HAS GROWN BY 600 PERCENT SINCE 1970 LOUISVILLE -- Kentucky's prison population has exploded by 600 percent since 1970 and will keep growing because of "irrational" penalties enacted by lawmakers, a new study says. The study by University of Kentucky law professor Robert Lawson, who wrote Kentucky's penal code, says the burden on taxpayers has increased exponentially in that time. The state's budget for housing state prisoners has risen from $7 million to more than $300 million over that same period and is threatening to bankrupt the system, Lawson wrote in the 72-page report. "We have demonized criminals in mass, lost sight of the importance of distinguishing between dangerous ... and non-dangerous offenders, and laid a foundation for a new citizen underclass made up of parolees, ex-convicts and their families," the report says. The number of inmates had climbed from 2,838 in 1970 to 17,330 by last year, according to the report. The report blames that rise on the state's "brutally harsh" persistent felon law and an array of drug penalties. The number of persistent offenders in Kentucky's prisons has grown from 79 in 1980 to 4,187 this year -- more inmates than were held in the entire system in 1970. Lawson says that the state must soften its persistent felon and drug sanctions in order to afford to house the flood of projected new inmates and free up resources for treating and training offenders. The study, titled "Difficult Times in Kentucky Corrections -- Aftershocks of a 'Tough on Crime' Philosophy," was compiled based on data provided by state agencies, Lawson said in an interview. It will be published next year in the UK's law review. The study suggests that Kentucky's "three strikes" law be tailored to cover only violent offenses for which the offender previously received prison time. Lawson says Kentucky's penal code is now one of the toughest in the nation as a result of "stupendous" changes enacted piecemeal over ensuing decades. It is one of only a few states, for example, that applies its persistent felon law to nonviolent offenses. "The three strikes law permits and sometimes even requires punishment that is morally indefensible ... and that works to warehouse for extended periods offenders who are unlikely to inflict serious harm on the public," Lawson's report says.