Bill Clinton’s now-controversial 1994 crime bill was at the center of a clash Thursday between the former president and protesters in Philadelphia in which Clinton defended the bill, saying it was the reason behind huge drops in crime rates by the end of his presidency.

"Because of that bill, we had a 25-year low in crime, a 33-year low in the murder rate, and listen to this," Clinton responded Thursday, "because of that and the background check law, a 46-year low in the deaths of people of gun violence. And how do you think those lives were, that mattered? Whose lives were saved, that mattered?"

But can the decreases in crime since the late 1980s really be attributed to Clinton’s signature legislation? Here’s what we found.

During Bill Clinton’s campaign stop for his wife in Philadelphia on April 7, a protester with the Philadelphia Coalition for Real Justice yelled questions at the former president while another held a sign that read "Clinton crime bill destroyed our community."

The protester, later identified as Erica Mines, criticized the 1994 Violent Crime Control and Law Enforcement Act that provided for higher federal funding for prison facilities that some say ushered in mass incarceration in America.

The former president continued defending the bill, asking the protesters whether they were really defending criminals.

"I don’t know how you would characterize the gang leaders who got 13-year-old kids hopped up on crack and sent them out into the street to murder other African American children," he told the protesters. "Maybe you thought they were good citizens — [Hillary Clinton] didn’t."

At a campaign stop the next day in Erie, Pa., Bill Clinton issued an apology of sorts, saying he "rather vigorously defended" his wife.

"I did something yesterday in Philadelphia," he said, according to MSNBC. "I almost want to apologize for it, but I want to use it as an example of the danger threatening our country."

In addition to prison funding, the crime bill also expanded the use of the death penalty, provided states with incentives to implement harsher sentences on criminals and established the Community Oriented Policing Services program, which provided grants to fund up to 75 percent of new police hires for three years.

As Bill Clinton said, the crime rate at the end of his presidency was the lowest in two decades and statistics published in a 2000 report on homicide trends from the Bureau of Justice Statistics show the murder rate had "declined to levels last seen in the late 1960s."

But experts say the decline in crime during Clinton’s time in the White House can’t all be attributed to the 1994 crime bill.

Crime rates nationally began to drop just before the passage of the crime bill, in 1992. Multiple academic reports on the topic begin with 1991 to trace when recorded incidents began to slip.

There are several factors, researchers find, that could have caused this fall in crime. In fact, researchers don’t entirely agree on which factors had the greatest impact. Our analysis can find this consensus: the drop cannot be solely attributed to the crime bill, and the size of the crime bill’s contribution, while arguable, may not be higher than a third, according to more favorable analyses, if not marginal overall, per more conservative accounts.

For starters, here are some other debated but commonly acknowledged factors. Through 1991 to 1993, the ‘90s boom began, creating more job opportunities in the low-wage sector. The impact of the the crack epidemic entering its death knell has also been cited. The crime bill created 100,000 new jobs for cops, but the number of police officers in the U.S. rose by 50,000 to 60,000 per capita over the decade, a 14 percent increase.

By the end of Clinton’s time in the White House, the number of incarcerated Americans rose by nearly 60 percent, according to figures from the Bureau of Justice Statistics.

A 2015 study by NYU’s Brennan Center for Justice found that "increased incarceration at today’s levels has a negligible crime control benefit." According to the researchers, increased incarceration accounted for about 6 percent of the drop in property crime in the 1990s and had little impact on nationwide decreases in violent crime.

Inimai Chettiar, the director of the Brennan Center’s Justice Program, said the crime bill’s investment in local police forces did contribute to a decrease in crime rates, but mass incarceration played a smaller role in driving decreases in crime. She suggested the the drops could also be attributed to improved technology in policing techniques and changes in social and economic factors like an aging population and a decrease in alcohol consumption.

Other studies also suggest mass incarceration leads to "diminishing returns," meaning the practice may have had a larger impact on decreasing crime rates when it was first implemented, but those results slowly decrease over time. A 2014 study from the Hamilton Project, an offshoot of the Brookings Institution, called mass incarceration and crime control "a classic case of diminishing marginal returns."

Marc Lamont Hill, a political commentator and professor of African American studies at Morehouse College, told CNN Thursday "there's absolutely no empirical evidence to suggest that crime bill was the causal factor that made crime go down."

"You can cherry pick anecdotes, a bunch of anecdotes together and it doesn't make it data," Hill said. "The data does not bear out."

Hillary Clinton has somewhat separated herself from her husband’s legislation.

"It's time to change our approach," she said during a talk on criminal justice last year. "It's time to end the era of mass incarceration. We need a true national debate about how to reduce our prison population while keeping our communities safe."

Bill Clinton’s defense of the crime bill comes less than a year after he appeared at a national convention for the NAACP when he issued a mea culpa of sorts over his own bill.

"I signed a bill that made the problem worse," he said in July 2015 in Philadelphia. "And I want to admit that."

Our ruling

In a heated exchange with protesters in Philadelphia, Bill Clinton defended his 1994 crime bill saying "because of that bill, we had a 25-year low in crime, a 33-year low in the murder rate, and listen to this, because of that and the background check law, a 46-year low in the deaths of people of gun violence."

Experts and studies haven’t reached consensus on what caused the historic drops in crime. But they do roundly agree that it can’t all be attributed to Clinton’s 1994 crime bill. In fact, most suggest the crime bill’s role in the drop was negligible. We rule the claim Mostly False.