WASHINGTON — Reacting to the Arizona shooting with anger, sadness and shock, a majority of Americans think that suspect Jared Loughner should be sent to death row if he’s convicted, according to one poll. But if statistics are any indication, he has a good chance of escaping execution.

Federal prosecutors have had little luck persuading juries to send defendants to death row. Of 467 defendants whom U.S. attorneys general in Washington have authorized to face the federal death penalty since it was instituted in 1988, only 15 percent have received it.

The list of criminals who’ve escaped federal death row includes high-profile convicted killers: Unabomber Ted Kaczynski, Oklahoma City bomber Terry Nichols and Olympic Park bomber Eric Rudolph.

Experts say the cases reveal something about the death penalty that Loughner’s attorneys undoubtedly will use to their advantage: Once juries or prosecutors know the details of suspects’ lives and circumstances — even in the most heinous cases — they can be hesitant to mete out the ultimate punishment. When questions are raised about the defendant’s mental state, as in Loughner’s case, that decision can be even more difficult, even for staunch supporters of the death sentence.

“”It’s one thing in the abstract to say you’re for the death penalty,”” said Gerald Zerkin, a senior assistant federal defender in Richmond, Va., who’s represented several defendants charged with capital crimes, including convicted Sept. 11 plotter Zacarias Moussaoui. “”It’s something else entirely to hand down a death sentence.””

Although the Justice Department is weighing the death penalty for Loughner, defense attorneys might persuade prosecutors to seek life in prison to avoid trial. More than 40 percent of the cases that U.S. attorneys general approved for the death penalty were settled out of court, according to the Federal Death Penalty Resource Counsel Project. Many times, prosecutors are convinced not to seek the death penalty because the victims’ relatives wish to avoid trial, experts said.

But Aitan Goelman, a former federal prosecutor who helped prosecute the Oklahoma City bombing case, said Attorney General Eric Holder undoubtedly would feel pressure to seek the death penalty given that a congresswoman was shot and six people were killed, including a federal judge and 9-year-old girl.

“”If you have the federal death penalty and you don’t seek it in this case, what case do you seek it in? Goelman asked.

Goelman, however, acknowledged that it would be a tough call for prosecutors because of the way federal law is written. “”It bends over backwards to give the defendant the benefit of the doubt,”” he said.

In Loughner’s case, evidence has emerged that could tip the balance in either direction.

Prosecutors might seek the death penalty because of indications that Loughner carefully planned out the failed assassination of Rep. Gabrielle Giffords. On an envelope the FBI found, he’s said to have written of the shooting: “”I planned ahead.””

However, defense attorneys are expected to argue against the death penalty by pointing to evidence that he’s mentally ill. Before the shooting, a college professor and fellow student complained about Loughner’s strange behavior and his college eventually booted him for such concerns.

Under federal law, prosecutors and juries are required to weigh such evidence. At the sentencing stage, “”there’s no bright line”” in determining when mental illness is enough of a factor to save someone from the death penalty, said David Bruck, a clinical professor of law at the Virginia Capital Case Clearinghouse.

“”It is very rare for someone to be acquitted by reason of insanity,”” he said. “”But it is extremely common for people to avoid the death penalty because of their mental illness.””

Loughner’s lead attorney, Judy Clarke, helped save Kaczynski and Rudolph from the death penalty. She worked on the defense team that won over the sole juror responsible for keeping Moussaoui off death row.

In a lesser-known case that might have stronger comparisons to Loughner, Clarke convinced federal prosecutors to reverse course after they’d already authorized the death penalty for Buford Furrow Jr.

Furrow, an avowed white supremacist, murdered a postal carrier and shot and wounded five people at a Jewish community center. Clarke pieced together a timeline of his life demonstrating how serious mental illness had fueled his irrational behavior — not racism, Bruck said.

She might be able to demonstrate a similar pattern in Loughner’s case, Bruck said.

“”If that were to bear out, it would be surprising to see the government insist on seeking the death penalty,”” Bruck said. “”They’re not supposed to call this differently because there’s political pressure or a public outcry.””

Nonetheless, former prosecutors and other experts said it was difficult for Justice Department officials to ignore calls for the death penalty in high-profile cases, especially for a Democratic administration that might be sensitive to accusations of being soft on criminals.

Paul Charlton, who was a U.S. attorney in Arizona during the George W. Bush administration, accused then-Attorney General Alberto Gonzales of ignoring his recommendation to seek life in prison instead of death in one case.

Charlton, a Republican appointee who favors the death penalty in some cases, said there were witnesses in the case but not enough forensic evidence to pursue the death penalty.

“”Because we were seeking the ultimate penalty, I felt we needed evidence that doesn’t forget, doesn’t lie,”” he said this week in an interview.

Charlton said Justice Department officials felt they had to pursue the death penalty to appease conservatives, an assertion that Gonzales denied. Charlton was one of nine U.S. attorneys whom Gonzales fired in 2006 in a scandal that later led him to resign.

Charlton convinced Gonzales’ replacement, Attorney General Michael Mukasey, to reverse the decision.

Loughner also could face state capital charges before a jury in Pima County, Ariz., where the shooting occurred.

But Dale Baich, an assistant federal public defender in Arizona who handles death penalty cases, said Pima County juries historically were less likely to seek the death penalty than juries in the Phoenix metropolitan area, which has one of the highest death-sentence rates in the country. Although Arizona has a higher-than-average death penalty rate, the number of capital cases pending in the state declined from 155 in 2008 to 102 in 2010, according to Arizona’s Capital Case Oversight Committee.

State juries tend to hand down more death penalty verdicts than federal jurors do. Experts say one reason for that is that federal defense attorneys are more experienced and better trained than their state counterparts are.

Even so, the number of incoming convicts in the nation’s prisons facing execution has dropped 51 percent since 2000.