The Senate Judiciary Committee approved the Smarter Sentencing Act of 2013 by a wide margin Thursday, taking a major step toward reducing mandatory drug-related sentences. Amendments attached to the bill, however, would also establish new mandatory sentences for sex crimes, domestic violence and terrorism.

The bill is sponsored by Senate Majority Whip Dick Durbin, D-Ill., and Sen. Mike Lee, R-Utah, and has significant bipartisan support. Its primary aim is to allow greater sentencing flexibility and would reduce various drug-related mandatory minimums from five, 10 and 20 years to two, five and 10 years. It would also allow prisoners with crack cocaine convictions to have their punishments revisited in light of the 2010 law that lessened penalties for the drug.

In a frustrating blow to some reformers, committee members adopted three amendments from Sen. Chuck Grassley, R-Iowa, that would add the new minimum sentences.

Committee members voted 15-3 to establish a mandatory minimum sentence of five years for federal sexual abuse crimes and 15-3 to created a 10-year mandatory minimum sentence for interstate domestic violence resulting in death of the victim.

Sens. Patrick Leahy, D-Vt., Mazie Hirono, D-Hawaii, and Lee voted against those amendments.

"Our research shows for the specific crimes they were targeting, those mandatory minimums were considerably lower than the average sentence for that type of crime," says Brian Phillips, Lee's communications director.

In addition to viewing them as unnecessary, Lee voted against the proposals "to be consistent on principle when it comes to mandatory minimums [and] to the purpose of this bill, which is much more narrow than some are trying to make it," Phillips says.

Hirono's decision to vote no was based in part on opposition from the National Task Force to End Sexual and Domestic Violence, which said in a Thursday letter to lawmakers there are better ways to protect abuse survivors and punish offenders.

"[E]ach case and each victim's situation is so unique, it is our opinion that the establishment of mandatory minimum sentences in these cases does not necessarily ensure the safety of victims of these crimes," the task force letter said.

Committee members approved a new five year mandatory minimum sentence for providing arms to terrorists by a voice vote.

The overall bill was approved 13-5 by the Senate Judiciary Committee. All 10 committee Democrats and Republican Sens. Ted Cruz of Texas, Jeff Flake of Arizona and Lee voted in favor.

The American Civil Liberties Union, a prominent supporter of rescinding mandatory minimums, is displeased with the possibility of new mandatory sentences.

"What we're trying to do is untie judges' hands and these three amendments tie them further," says Laura Murphy, director of the ACLU's Washington Legislative Office.

Murphy says the ACLU will continue to support the overall bill, but will also seek the removal of the amendments when the bill is considered on the Senate floor.

"It is really disheartening that the Grassley amendments were added," Murphy says. "I don't think there's any doubt that people who commit sexual offenses get hard time and so I don't understand the necessity."

Murphy says it's probable the new minimums would affect a small number of people relative to the drug crimes – as many sexual offenders are prosecuted under state law – but says the issue remains a significant concern.

"The basic question is, should these penalties be given based on individual circumstances and allowing federal judges to use their discretion, or do judges go back to being forced into a robotic response?" she says.

Jesselyn McCurdy, senior legislative counsel at the ACLU, says "it's going to be an uphill battle" to remove the new minimums.

"We have to catch our breath to think up a strategy," McCurdy says.

It's currently unclear how many people are charged annually with the sexual crimes that would be affected, but preliminary research by the ACLU suggests several hundred people are charged annually with the offenses.

Families Against Mandatory Minimums, a group supporting sentencing reform, also expressed concern about the new minimums.

"We strongly support the underlying bill; however, we have deep concerns about changes made during markup," FAMM President Julie Stewart said in a statement. "These changes include new mandatory minimums for domestic violence and sexual abuse that are unjustified and opposed by the very victims they are supposed to protect."