Deondre Pleasant is familiar with the institutions belonging to Kentucky's Department of Corrections (search) — some would argue, far too familiar.

"I'm serving an 18-year sentence. And actually, I've been out repeatedly and come back," Pleasant said.

Pleasant is one of 18,000 inmates doing time in the state system, many of whom are just like him in that they're jailed for committing the same crime more than once. In Pleasant's case, the crimes involved drugs.

Ever since Kentucky rewrote its criminal laws in the 1970s, its inmate population has grown more than 600 percent. Prisons are nearly packed to capacity.

"Its a matter of changing policies, longer sentences. We're incarcerating huge numbers of people for drug offenses," said Robert Lawson, a professor at the University of Kentucky law school who wrote the state's current penal code.

Lawson said the primary reason the inmate population is growing so rapidly is because of the way Kentucky uses its "three-strikes" law (search). The purpose of the law is to punish violent offenders with longer sentences for repeating their crimes, he said.

But even committing three minor offenses can put someone behind bars for decades.

"It applies to all the drug offenses, it applies to property crimes, even disorderly crimes," Lawson said.

Kentucky Attorney General Gregory Stumbo (search) said the three strikes law is a deterrent.

"The law is designed to keep bad actors in jail and if bad actors means you continue to break the same law over and over again, then yes, that's what its designed to do," Stumbo said.

He cited a study showing that violent crimes dropped 45 percent in California since that state enacted its three-strikes law a decade ago. Twenty-three states now have some form of a repeat-offenders' law.

"The catch-and-release program ought to be for fish and not for felons," Stumbo said.

But Lawson said that if Kentucky keeps adding inmates at its current pace, the state will have to raise taxes to pay for the increased costs.

Stumbo said correctional costs are 4 percent of the overall state budget, a small price to pay for keeping criminals off the streets.

Click in the box near the top of the story to watch a report by FOX News' Jeff Goldblatt.