President Barack Obama on Wednesday cut short prison time for eight drug convicts as part of his new initiative to reduce harsh sentences under outdated guidelines, a step that could lead to a vast expansion of presidential clemency in his final two years in office.

The president also is pardoning 12 convicts for a variety of offenses. But the commutations are particularly significant because they are the first issued under new guidelines announced this year designed to cut costs by reducing the nation’s bulging prison population and grant leniency to nonviolent drug offenders sentenced to double-digit terms.

A pardon forgives a crime without erasing the conviction, typically after the sentence has been served. A commutation leaves the conviction and ends the punishment.

The White House said the eight new commutations Obama granted were for prisoners who likely would receive a substantially lower sentence today and would have already served their time. For example, they include Barbara Scrivner, who was sentenced to 30 years in 1995 when she was 27 years old for a minor role in her husband’s meth ring. Obama ordered her sentence to expire June 12, while others will expire April 15.

Administration officials say they expect Obama to grant more clemency petitions in his final two years in office under the changed policy he ordered from the Justice Department. The White House said 6,561 people already have applied in the past year, compared to 2,370 the year before.

“I think there is an awareness out there that this president is interested in granting clemency on these kinds of matters,” White House counsel Neil Eggleston said in an interview.

The clemency policy changes aren’t limited to drug offenders, who comprise about half of the roughly 216,000 federal prisoners, but the criteria makes it clear they are the main target.

To be eligible, inmates must have already been behind bars for at least 10 years, have a nonviolent history, have no major criminal convictions, have a good behavior record in prison, and be serving a sentence that, if imposed today, would be substantially shorter than what they were given at the time.

Facebook Twitter Pinterest A prisoner. Photograph: John Moore/Getty Images

The old sentencing guidelines subjected tens of thousands of blacks to long prison terms for crack cocaine convictions while giving far more lenient sentences to those caught with powder who were more likely to be white. It was enacted in 1986 when crack cocaine use was rampant and considered a particularly violent drug. Under that law, a person convicted of possessing five grams of crack cocaine got the same mandatory prison term as someone with 500 grams — 100 times — of powder cocaine.

The president signed the Fair Sentencing Act in 2010 to cut penalties for crack cocaine offenses in order to reduce the disparity. But the act addressed only new cases, not old ones.

In his first term, Obama commuted just one drug sentence and pardoned 39 people, causing prisoner advocates to accuse him of being too stingy with his power. Obama aides said it was because he wasn’t receiving more positive recommendations from the Office of the Pardon Attorney so he directed the Justice Department to improve its clemency recommendation process and recruit more applications from convicts.

Deputy Attorney General James Cole, who in April announced the clemency policy changes, said the sentence commutations reflect a “commitment to bring fairness to our criminal justice system.”

“While all eight were properly held accountable for their criminal actions, their punishments did not fit their crimes, and sentencing laws and policies have since been updated to ensure more fairness for low-level offenders,” he said in a statement.

The Bureau of Prisons has been notifying inmates of the new criteria and encouraging applications from those who qualify. The Justice Department has asked bar associations around the country to help prepare their petitions.

The White House noted Obama now has commuted 18 sentences, compared to 11 under President George W. Bush and three in the first six years of the Clinton presidency. Clinton eventually commuted 61, most in a controversial action on his last day in office.