Criticism of authorities for not launching a deeper investigation of the Army major charged in the Fort Hood massacre has increased scrutiny of the pace of inquiries into terrorism risks.

At least 18 e-mails were intercepted between Maj. Nidal Malik Hasan and a radical Muslim cleric. The way the FBI handled the information about Hasan before the shooting rampage is being reviewed.

Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary's University in San Antonio, said he has noticed investigators have been more cautious in the last few years.

"I think the reason we were a bit trigger-happy was Sept. 11, but we're starting to get more patient," he said.

Pursuing charges before all the evidence is in hand can backfire – suspects have sued authorities before, claiming they were falsely imprisoned victims of witch hunts.

Federal investigators have a mixed record when other terrorist plots have been broken up early.

Five Muslim immigrants were convicted last year of conspiring to kill U.S. soldiers at Fort Dix in New Jersey, but they were acquitted of attempted murder after prosecutors acknowledged they were probably months away from acting.

Despite criticism sparked by the Fort Hood shootings, the FBI has had recent successes that officials credit to taking a methodical approach.

In Dallas, Hosam "Sam" Smadi, a 19-year-old Jordanian who the FBI says tried to blow up a downtown Dallas skyscraper, was arrested in September only after the FBI orchestrated a sting operation.

According to an FBI affidavit, agents had learned of Smadi months before through their monitoring of extremist Web sites. Smadi, of Italy, Texas, has pleaded not guilty.

FBI officials use a recent Atlanta case as an example of their success using a systematic approach.

In January 2006, agents watched as a young man suspected of links to terrorists walked out of an Atlanta Home Depot with materials that could be used to make a bomb.

They knew Syed Haris Ahmed had researched bombmaking techniques online and shaved his head, as some jihadis have done before an attack.

However, they decided to wait to arrest him and keep building a stronger case – and risk a potential terror attack.

They relied on federal explosive experts who told them the PVC pipe Ahmed bought was not enough to create a dangerous explosive. They also sent local police pretending to be on a routine call to question Ahmed about the piping.

"If we have a terrorist event, we could solve what happened. But that means we've lost," said Rick Maxwell, an assistant special agent in charge in Atlanta. "What we want to do is prevent them. It's much more difficult, but that's our goal."

Authorities made their move in early 2006, arresting Ahmed in March and co-defendant Ehsanul Islam Sadequee a month later in Bangladesh.

They were ultimately convicted of terror-related charges this year, and federal prosecutors said the case exemplified their strategy of snuffing out potential plots. Sadequee faces up to 60 years in prison, and Ahmed faces 15 years behind bars when the two are sentenced today.

As many as 150 people worked to carefully gather evidence that Sadequee met other extremists as he delved deeper into online forums devoted to jihad, said Greg Jones, the FBI's agent in charge in Atlanta.

When the two were convicted, a wave of relief washed over the investigators. But Jones said they wouldn't have waited if they knew something was going to happen.

"Public safety wins out every time," Jones said. "The slightest hint that an individual possesses something that can harm or kill, you let the case go to hell."

The Associated Press,

staff writer Jason Trahan