Sending someone to prison longer is no indication they'll be less likely to commit a crime once they're released, and longer sentences don't dissuade others from committing that crime, experts told lawmakers Monday.

In fact those legal and corrections experts said states that have reduced their prison populations the most have also seen a drop in the crime rate.

"Long sentences are not the panacea that many people think they are. They do not reduce crime, they do not increase public safety, and they cost the state a whole lot of money," said Professor Christopher Slobogin, director of the Criminal Justice Program at Vanderbilt University Law School.

"I think the common intuition, and it's a natural one, is 'hey, if we want to protect the public let's put them in as long as possible. But in fact the data show, and I think theory suggests, it doesn't make sense to do that."

The debate comes as the administration of Gov. Bill Haslam and lawmakers look at reforming how offenders are sentenced, when they may be eligible to leave prison and what they need to do once they are released. Although Haslam and lawmakers haven't put forward any specific plans, advocates and experts are worried any proposal to change when prisoners are released could lead to people unnecessarily spending more time in prison.

Slobogin was one of six people to testify at a Senate Judiciary Committee meeting after the state discussed the findings of a sentencing task force. Although Department of Safety and Homeland Security Commissioner Bill Gibbons read through the 16 recommendations, the majority of discussion focused on an idea to set a minimum amount of time served on a sentence.

Gibbons and others who testified acknowledged that under the current judicial system it's very hard to predict when someone will be released from prison. There is the length of a sentence, and what's known as a "release eligibility date," also called a RED date. For many offenses, that RED date comes at 30 percent of a sentence; for a 10-year sentence, the RED date could be three years.

However, any number of factors could move up or delay that RED date, Gibbons noted, as inmates can earn credit for good behavior or taking classes, and generally get credit for any time served leading to their trial. The state is considering a number of solutions to try and provide some predictability as to when an inmate might actually get out of prison.

One of those solutions would be to put the minimum mandatory sentence at the average amount of time offenders charged with similar crimes stay in prison. Slobogin and others said that's a bad idea: The average length of time served is always longer than an inmate's RED date, said Alex Friedmann, associate director of the Human Rights Defense Center and editor of Prison Legal News.

"If that's your minimum date, say 30 percent (of a sentence), then only 35 percent of people get out at that date," Friedmann said, referring to the typical inmate granted parole at their RED date.

"Necessarily, the average sentence served has to be higher than the RED date ... so once you average those together, the average sentence served is going to be elevated above that RED date."

Slobogin, Friedmann and others recommended the state set the RED date as the presumptive release date. It's one of the many issues they had with the state's task force on sentencing, but one they believe would immediately help.

Several lawmakers questioned that idea. Sen. Kerry Roberts, R-Springfield, said he thought there wasn't enough focus on the victims during the discussion of appropriate sentences. Sen. Janice Bowling, R-Tullahoma, suggested going as far as sending people to prison on a second committed offense for crimes such as burglary, as opposed to for a third offense, and denying someone the right to a public defender if they're accused of a crime they've committed in the past.

Slobogin argued longer sentences are longer now than in the past, and the crime rate isn't going down. In general he argued longer sentences can lead to an inmate being influenced to commit crimes while in prison and make it much harder for that person to reintegrate back into the community once he or she is released.

Senate Judiciary Committee Chairman Brian Kelsey, R-Germantown, said he was pleased with the discussion and glad everyone could agree there needs to be more predictable sentencing.

"I'm glad that we have reached a consensus that people do need to know on the front end what sort of time is going to actually be served," Kelsey said.

"In terms of which one of those dates to pick, I think there's still a lot of hard work that has to be done."

Kelsey said he hopes Haslam takes up something from the task force reform agenda. If he does, Kelsey said it would be the governor's "greatest achievement" next year. Session starts in January.

Inmate population in Tennessee

Christopher Slobogin, head of the Criminal Justice Program at Vanderbilt University Law School, argued longer sentences do not lead to safer states. He pointed to Tennessee's prison population and violent crime rate.

Tennessee prison population, per 100,000 U.S. residents:

1981: 171 inmates per 100,000 people

2013: 438 inmates per 100,000 people

In 2012, FBI statistics showed Tennessee had the highest violent crime rate in the nation.