The high court's decisions on the constitutionality of the two cases could affect the way death row inmates around the country are executed and how voters cast their ballots ahead of the 2008 elections.
In deciding the constitutionality of lethal injections, the Supreme Court will hear a challenge from Ralph Baze and Thomas Clyde Bowling Jr., two death row inmates in Kentucky who sued the state in 2004, claiming lethal injection violates the Eighth Amendment's ban on cruel and unusual punishment.
A state judge upheld the execution and the Kentucky Supreme Court affirmed that decision. Baze had been scheduled for execution Tuesday night.
Thirty-seven states perform lethal injections as a method for execution and use the same three-drug "cocktail" consisting of an anesthetic, a muscle paralyzer and a chemical to stop the heart. Death penalty opponents have argued that a condemned prisoner can suffer extreme pain without being able to cry if not enough anesthetic is injected.
"This is probably one of the most important cases in decades as it relates to the death penalty," David Barron, the public defender representing Baze and Bowling, told the Associated Press.
Baze was sentenced for the 1992 shooting deaths of a Powell County sheriff and deputy. Bowling was sentenced for the 1990 killing of a couple and the shooting of their 2-year-old son.
In the voter identification case, justices will hear arguments early next year in a challenge to an Indiana law that requires voters to present photo ID before casting their ballots.
The state has defended the law as a way to combat voter fraud, while the Indiana Democratic Party and civil rights groups argue that the law unfairly targets poor and minority voters.
The 2005 law was upheld by a federal judge and by the 7th U.S. Circuit Court of Appeals. Before the law's passage, an Indiana voter was only required to sign a poll book at the polling place, where a photo copy of the voter's signature was kept on file.
"The court has over and over stressed that the right to vote should be protected, and any state law that burdens that right should be carefully and meticulously reviewed," Bill Groth, an attorney who has represented the Indiana Democratic Party in the lawsuit, told the AP.
Courts have upheld voter ID laws in Arizona, Georgia and Michigan, but struck down Missouri's. The Supreme Court is expected to issue a decision by late June, in time for the November general election.