What's Inside the Controversial 1994 Crime Bill That's Plaguing Hillary Clinton on the Campaign Trail

Former President Clinton signed the multi-pronged bill into law.

Here's everything you need to know about the controversial law and why it's the subject of criticism now:

What the Law Did

Notably, the law helped pay for new federal prisons if states agreed to force offenders to serve 85 percent of their sentence as opposed to allowing them out early on parole.

"It looked on the books as if this was going to more than double the prison sentence lengths of offenders nationwide if the individual states would go for it," Professor Candace McCoy from John Jay College's Doctoral Program in Criminal Justice told ABC News.

"In actual impact, that law was considerably less severe than it appeared and that's because many states didn't go for it. The ones that did, such as New Jersey ... they applied it only to violent offenders. Well, most of those people were going to prison for very long times anyway so it increased the sentence lengths sometimes, but not much. They virtually abolished parole," she added.

One of the other more visible initiatives was the hiring of 100,000 more police officers across the country by paying for two-thirds of the new officers' salaries in participating cities.

There were many other facets to the law, but some of the most notable others are the creation of the federal "three strikes" rule, which mandated life in prison for people who had committed three violent felonies; the assault weapons ban, which stopped the manufacture of 19 semi-automatic firearms; and the removal of education grants for inmates.

Prompting Criticism Now

The law is largely criticized for causing incarceration rates to spike, particularly for minorities. But experts differ on the direct impact the crime bill had on mass incarceration.

Giacalone said that since so much focus was being paid to the crack epidemic at the time, one of polices' biggest targets were crack dealers, who were hit with longer sentences and higher fines. He conceded that the bill did cause prison rates to "balloon," noting "for every action of course there's a reaction."

But McCoy disagreed that the jump in mass incarceration was caused by the crime bill.

"It is not directly responsible for the worst excesses of mass incarceration or police militarization. It's simply not," McCoy said. "The mass incarceration came from the states, and Bill Clinton got on their bandwagon."

What the Clintons Have Said

"That was not as apparent at the time, but part of being a responsible decision maker is to keep track of what’s happening.... And now I think it’s clear there were some consequences that we do have to address," she told the paper's editorial board.

Last summer, former President Clinton made a similar statement, noting that he "signed a bill that made the problem worse."