What happens to captured spies?

(CNN) — What happens to spies once they’re caught?

The question is in the news after an Israeli official involved in talks told CNN that Jonathan Pollard could be released before the Jewish holiday of Passover as part of efforts to save Israeli-Palestinian peace negotiations.

Pollard was a U.S. intelligence agent convicted of spying for Israel.

Agents from other countries are usually traded, while American turncoats tend to get locked away. Here’s a sample from the Cold War era onward.

Jonathan Pollard

Now locked away for more than a quarter-century, Pollard is a divisive figure in U.S.-Israeli relations. The former U.S. Navy intelligence analyst was caught spying for Israel in 1985 and was sentenced to life imprisonment in 1987. The United States and Israel are discussing his possible release as part of efforts to save fragile Middle East peace negotiations, according to sources familiar with the talks.

Francis Gary Powers

During the late 1950s, the CIA flew high-altitude U-2 spy planes over the Soviet Union on a regular basis — until one of them was shot down in 1960. Its pilot, Francis Gary Powers, was captured. After the United States denied any involvement, both Powers and the wreckage of his aircraft were put on display in Moscow. Tried and convicted of espionage, he was traded for convicted Soviet spy Rudolf Abel in 1962.

Valdik Enger and Rudolf Chernyayev

Covert KGB officers Enger and Chernyayev got ensnared in a 1977 sting operation run by the FBI and the U.S. Navy. They were arrested after taking the bait from an American double agent, convicted of espionage and traded for five Soviet dissidents in 1979. The FBI credits “Operation Lemon-Aid” with giving U.S. authorities a great insight into how Soviet operatives maneuvered in the United States.

John Walker

Walker ran a father-and-son spy ring from 1967 to 1985. He was a Navy communication specialist with financial difficulties when he walked into the Soviet Embassy and sold a piece of cyphering equipment. Defense officials said that Walker enabled the Soviet Union to unscramble military communications and pinpoint the location of U.S. submarines at all times. As part of his plea deal, prosecutors promised leniency for Walker’s son Michael Walker, a former Navy seaman.

Ronald Pelton

Pelton joined the super-secret National Security Agency, the U.S. government’s electronic intelligence arm, after serving in the Air Force’s communications intelligence division. He resigned in 1979, but after running into financial trouble, he approached the Soviet Embassy in Vienna. He then began passing Moscow classified information, including details of a program that tapped undersea Soviet communications cables. He was exposed when his handler defected to the United States in 1985, and he’s still serving a life sentence at age 72.

Aldrich Ames

Ames, a 31-year CIA employee, pleaded guilty to espionage charges in 1994 and was sentenced to life in prison. Ames was a CIA case worker who specialized in Soviet intelligence services and had been passing classified information to the KGB since 1985. U.S. intelligence officials believe that information passed along by Ames led to the arrest and execution of Russian officials they had recruited to spy for them.

Earl Pitts

Pitts’ job was to monitor suspected Soviet spies at the United Nations. But the veteran FBI agent soon began selling his secrets to the KGB, which he contacted in 1987, and its successor agencies after the Soviet Union collapsed. He got about $224,000 from the Kremlin before a Russian double agent tipped off U.S. intelligence, and he was arrested in 1996. The federal judge who sentenced him to 27 years in prison — more than prosecutors had requested — told him, “You betrayed your country, you betrayed your government, your fellow workers and all of us, really.”

Robert Hanssen

Hanssen began spying for the Soviet Union in 1979, three years after going to work for the FBI. Prosecutors said he collected $1.4 million for the information he turned over to the Cold War enemy. In 1991, he broke off relations with the KGB — but resumed his espionage career in 1999, this time with the Russian Intelligence Service. He was arrested after making a drop in a Virginia park in 2001 and pleaded guilty to espionage charges in exchange for a life sentence.

Anna Chapman & Co.

It had an echo of Cold War spy novels: Russian agents living seemingly normal lives in the New York area, waiting for orders from Moscow. Arrested after years of investigation by FBI agents, 10 so-called illegals were traded for four Russians who had been convicted of spying for Western powers at Vienna’s airport in 2010. One of the spies — an attractive redhead named Anna Chapman — went on to become a celebrity in Russia, modeling lingerie and serving on the board of the youth arm of President Vladimir Putin’s ruling party.