The Supreme Court is expected this week to announce decisions on three potentially landmark cases, two of which would expand the rights of gays and lesbians in the country and another that could change how the nation votes in federal elections.

As the high count enters what is expected to be the final week of its current session, justices have a range of options on how to handle the three cases -- particularly the challenges to the Defense of Marriage Act, or DOMA, and California's Proposition 8 ban on same-sex marriage.

DOMA, the more far-reaching of the two marriage laws, was enacted in 1996 and defines marriage as the union of a man and a woman. The law keeps legally married gay Americans from collecting a range of federal benefits that generally are available to married people.

While the Clinton and Bush administrations backed the law, President Obama in 2011 instructed the Justice Department to stop defending it. House Republican leadership then stepped in to bankroll DOMA's defense, spending about $3 million.

California voters in 2008 approved Proposition 8, which later was ruled unconstitutional by an appeals court. Like DOMA, the state has refused to defend it.

The justices could issue simple up-or-down rulings on the marriage cases, or they might opt for something narrow and legalistic.

Or the high court could take a page from its Monday ruling on a Texas affirmation action case and return the case to the lower courts.

Russell Wheeler, a legal expert with the Brookings Institution, a prominent Washington think tank, said it's likely the court will strike down both marriage laws, saying justices may fear being on the wrong end of history.

"Some members of the court -- the so called liberal block, Justice Roberts, Justice Kennedy -- may well be concerned about how they look in some historical perspective," Mr. Wheeler said.

"I think people may well be asking 20 years from now what were they thinking trying to ban same sex marriage ... and some of justices may not want to be looked [at in the same light as prior Supreme Court justices] who fought school desegregation and other things."

But Wheeler added he wouldn't be surprised if the justices side-step the issues and "go on some procedural direction," such as kicking the issue back to the lower courts.

Jamin Raskin, a constitutional law professor at the American University Washington College of Law, also said he expects the court to strike down both DOMA and California's same-sex marriage ban.

"I think the court recognizes there needs to be a substantive ruling on the Defense of Marriage Act," he said. "There are just too many questions that come up in saying that gay people who are married in states that allow [gay marriage] don't enjoy equal rights and benefits of straight couples."

If the marriage laws are struck down, that wouldn't mean gays and lesbians have the constitutional right to marry. But it would keep state-level same-sex marriage laws in place and set up a legal pathway for more states to do so.

The Supreme Court also is expected to announce its ruling on a case that could end a landmark Civil Rights-era law designed to combat discriminatory voting practices nationwide.

All or parts of 16 states, mostly in the South, must receive approval from the Justice Department or a federal court before making changes in the way they hold elections. The provision is part of the 1965 Voting Rights Act -- enacted to stop Jim Crow-era practices such as literacy tests, poll taxes or other measures designed to keep blacks from voting.

But Shelby County, Ala., is challenging the constitutionality of the advance approval, or "preclearance" requirement, saying it no longer should be forced to live under oversight from Washington because it has made significant progress in combating voter discrimination.

The county -- a mostly white suburb of Birmingham -- also argues that preclearance is an encroachment on state sovereignty.