Shortly after Osama bin Laden was killed in May, the FBI sent out a request to its field offices to nominate candidates who could fill bin Laden's place on the bureau's "Ten Most Wanted Fugitives" list.
The choice is more complicated than simply finding a violent criminal who has committed a high-profile crime.
In recent years, bureau officials have also tried to select other dangerous fugitives who may have been hiding in plain sight but could be recognised by the public because they have distinctive physical features.
On Tuesday, the FBI finally filled bin Laden's place on the list, adding Eric J. Toth, a schoolteacher from the Washington area accused of possessing child pornography.
The announcement marked the first time since 2009 that the FBI had added a fugitive to the list.
"We have had a couple of vacancies on the list that we've been trying to fill," said Kevin L. Perkins, the FBI's acting executive director for criminal and cyber operations, referring to the spots left by bin Laden and the Boston crime boss James (Whitey) Bulger, who was arrested in June.
In fact, just last month, officials were preparing to ask the bureau's director for approval to choose a fugitive accused of killing three police officers in Puerto Rico.
But then that person was caught.Using most-wanted posters to enlist the public's help in catching criminals dates to the early part of J. Edgar Hoover's tenure as the head of the FBI in the early 1930s, when the face of the notorious bank robber John Dillinger was on a "public enemies list."
In 1950, the bureau began using the list of "Ten Most Wanted Fugitives". The first, Thomas Holden, was accused of killing his wife and two brothers-in-law. A little more than a year later, he was caught and ultimately sent to prison on Alcatraz Island in San Francisco.
Since then, the FBI has caught 464 of 494 fugitives on the list. Some have been captured quickly - Billie Austin Bryant, wanted for the murder of two FBI agents, was apprehended in 1969 just two hours after being added. A suspect in an armed robbery, Victor Manuel Gerena, has evaded authorities since 1983.
As US society has changed, so too has the list. For decades, the FBI list was displayed in post offices. But as the number of postal patrons has dropped, the bureau put the list on social networking sites like Facebook and Twitter, and on billboards.
"It's a big country, and you can easily hide if you are a fugitive," said Thomas W. Repetto, the author of several books on crime and policing. "But when you get on the list, you are pretty close to getting caught. Sometimes it takes time, but if you are fleeing criminal it is not a good place to be."
Reuters