The vote, expected late Thursday, is being closely watched by anti-abortion and other conservative groups, who have made passage of the Unborn Victims of Violence Act one of their top goals this year. Abortion rights groups say the bill is a blatant effort to undermine a woman's right to choose.
The bill,, states that an assailant who attacks a pregnant woman while committing a violent federal crime can be prosecuted for separate offenses against both the woman and her unborn child. The legislation defines an "unborn child" as a child in utero, which it says "means a member of the species homo sapiens, at any stage of development, who is carried in the womb."
"This bill recognizes that there are two victims," said Sen. Mike DeWine, R-Ohio, a chief sponsor. "It's as simple as that."
President Bush strongly supports the bill.
The Senate was considering two amendments to the bill. One, by Sen. Patty Murray, D-Wash., would require employers to give unpaid leave, and states to pay unemployment benefits, to women when they or family members are victims of domestic or sexual violence.
More pivotal was an amendment by Sen. Dianne Feinstein, D-Calif., that would impose tougher penalties for injuring or killing a pregnant woman and her fetus but classify such attacks as a single-victim crime, avoiding the issue of fetal rights and the question of when a fetus attains personhood.
Feinstein said her provision obtains the same law enforcement goals "without injecting the debate of a woman's right to choose into the equation."
The bill would go directly to the president for his signature if the two amendments are rejected.
Supporters of the bill have also named it after Laci Peterson and her unborn child Conner, victims in the highly publicized murder case in California. California, one of 29 states with a state unborn victims law, is trying Peterson's husband Scott on double murder charges.
The Senate bill covers 68 federal crimes of violence, such as drug-related shootings, violence at an international airport, terrorist attacks, crimes on a military base or threats against a witness in a federal proceeding.
It would specifically exclude prosecution of legally performed abortions — a fact supporters cite in arguing that the bill would not undermineaffirming a woman's right to end a pregnancy.
"The criminals who commit these crimes are not committing abortions," said Douglas Johnson, legislative director of the National Right to Life Committee. "They are depriving these unborn children of the right to life. It's a separate issue related to the right to life."
Groups on both sides of the abortion issue lobbied hard on the legislation. Johnson's group noted that family members — including Laci Peterson's mother — who had lost loved ones in attacks on pregnant women were in Washington to urge senators to pass the bill.
The Christian Coalition of America said votes for either the Murray or Feinstein amendments would be regarded as negative votes on its annual congressional scorecard of lawmakers.
On the other side, NARAL Pro-Choice America delivered more than 130,000 petitions to senators urging defeat of the bill because the group said it would allow judges to rule that humans at any stage of development deserve protection, even when that protection trumps a woman's interest in ending a pregnancy.
"This would be the first time in federal law that an embryo or fetus is recognized as a separate and distinct person under the law, separate from the woman," said NARAL president Kate Michelman. "Much of this is preparing for the day the Supreme Court has a majority that will overrule Roe v. Wade."