Attorney General Jeff Sessions recently charged federal prosecutors with taking a more aggressive approach to charging defendants, including seeking mandatory minimum sentences.

The guidelines, signed on May 10, 2017, moved in a very different direction from what the Department of Justice had been doing under President Barack Obama.

Under Obama, the department focused on prosecuting the most serious criminals and finding ways to keep minor or low-level offenders from serving long, mandatory sentences.

During a May 18 floor speech, Senate Minority Leader Charles Schumer, D-N.Y., made clear that he thought Sessions’ new guidelines were ill-advised.

"Thanks in part to this initiative, President Obama became the first president since (Jimmy) Carter to leave the White House with a smaller federal prison population than when he took office," Schumer said.

We wondered if that comparison was correct.

When we checked with Schumer’s office, a spokesman pointed us to research by the Pew Research Center, a widely trusted independent source.

Pew looked at federal Bureau of Prisons data going back to the 1920s and produced this graph showing a sharply increasing federal prison population between about 1980 and 2010.

The graph shows that not only was Obama the first president to see a drop in the federal prison population since Carter, but that only four other presidents (Johnson, Kennedy, Truman and Hoover) oversaw a decline on their watch. Most of the presidents studied -- nine, starting with Coolidge and ending with George W. Bush -- oversaw inmate increases on their watch.

We wondered whether Schumer was cherry-picking data from the much smaller pool of federal inmates. In 2015, the number of inmates in state-run prisons was almost seven times larger than the number of federal inmates, and the total number of inmates in state and local facilities was more than than 10 times larger than the number in federal custody.

However, we found that the same trends held for state and local inmate populations -- the number declined under Obama for the first time since at least the Carter years.

Here are the trend lines for state inmates (dark blue) and local inmates (lighter blue), which we compiled from federal prison statistics:

Meanwhile, a credible argument can be made that Obama’s policies made a difference in driving the decline.

As we’ve reported, Obama signed the Fair Sentencing Act of 2010 into law. It dramatically reduced a 100-to-1 sentencing disparity between powder and crack cocaine. And his administration advocated for, and the U.S. Sentencing Commission approved, the retroactive application of some of the new sentencing guidelines.

Ironically, Sessions was among a number of Senate Republicans who spoke in favor of the Fair Sentencing Act of 2010. "I will not favor alterations that massively undercut the sentencing we have in place, but I definitely believe that the current system is not fair and that we are not able to defend the sentences that are required to be imposed under the law today," he said in a 2009 Senate speech about the bill.

James Alan Fox, a criminologist at Northeastern University, said he sees no significant omissions from Schumer’s statement. "The assertion is correct," Fox said. "The reasons are partly strategic and partly being in the right office at the right time.

"During Obama's administration, prosecutors were discouraged from seeking unnecessarily long prison sentences for non-violent drug offenders, a practice that the Trump administration wants to change. In addition, the cumulative impact of a declining crime rate had an impact on prison populations."

Our ruling

Schumer said, "President Obama became the first president since Carter to leave the White House with a smaller federal prison population than when he took office."

The statistics bear out Schumer’s assertion, so we rate it True.