WASHINGTON (Reuters) - Controversy at home and abroad over the execution of Troy Davis, who was put to death in the United States late on Wednesday for the 1989 killing of a policeman, has renewed questions about the death penalty.
The U.S. Supreme Court rejected his last-minute plea for a stay of execution, and Davis, 42, received a lethal injection at a prison in Georgia.
"The Troy Davis case is going to bring a lot of doubt into people's minds," said Fordham University law professor Deborah Denno, an opponent of the death penalty.
"It gradually erodes the death penalty more and more ... public opinion is changing," she said.
Defense attorneys had argued Davis was innocent, citing new evidence and witnesses who had changed or recanted their testimony, some even saying another man committed the crime. No physical evidence linked Davis to the killing.
All the judges who reviewed the case rejected Davis's claim of innocence, upholding his conviction and death sentence.
Other death-penalty cases have included claims of innocence, like those raised by Davis, and racial claims. A defense attorney said a disproportionate number of inmates in Georgia's prisons and on death row were black men, as was Davis. The victim was white.
A Pew Research Center opinion poll in 2010 found that most Americans -- some 62 percent -- supported the death penalty for convicted murderers but Pew's Michael Dimock said the figure had declined slowly over the last 15 years. The polls show a drop from about 80 percent in the early 1990s.
The United States is the only western nation on an Amnesty International list of the 23 countries that imposed the death penalty last year. The countries were mainly in the Middle East and Africa, and China was believed to have the highest number of executions, followed by Iran and North Korea.
The U.S. Supreme Court, with a conservative majority, generally has supported the death penalty and shows no sign of placing a moratorium on executions any time soon. The court reinstated the death penalty in 1976 after a four-year moratorium.
The number of executions in the United States generally has been trending downward from a high of 98 in 1999. There were 46 executions last year and 35 so far this year, according to the Death Penalty Information Center.
Richard Dieter of the center, a Washington-based group which opposes capital punishment, said the battle will focus on individual states.
Thirty-four of the 50 states have the death penalty, along with the U.S. government and the U.S. military.
"At some point, the Supreme Court might find that the standards of decency regarding this punishment have shifted, but for now the focus is on state reforms or state abolition," Dieter said.
"Litigators will continue to fight for their individual clients, raising all the possible issues they can. Activists will seize on a few of those cases because they illustrate the broader problems that the death penalty presents," he said.
Nearly 1 million people signed an online petition against the execution. Pope Benedict, Nobel Peace Prize winner Desmond Tutu and former U.S. President Jimmy Carter were among those to express concern about the fairness of Davis's trial.
Despite attracting international attention, the case generated little comment from U.S. politicians, Republicans and Democrats alike.
Texas Governor Rick Perry, the frontrunner in the race for Republican presidential nomination in 2012, has presided over more executions than any of his peers since the death penalty was reinstated in 1976.
He received enthusiastic applause from the audience at a debate of Republican presidential candidates in California this month when he strongly defended his state's record in meting out what he called the "ultimate justice".
Supporters of the death penalty, such as Kent Scheidegger of the Criminal Justice Legal Foundation in California, said a federal judge a year ago rejected the claims by Davis as "smoke and mirrors."
"The Davis PR machine managed to whip up a froth of outrage anyway," he said in a blog post. "Large numbers of people have a grossly distorted view of the facts of this case, and that is not good."
Additional reporting by Matthew Bigg in Atlanta; editing by Howard Goller and Mohammad Zargham