In a seemingly extensive and highly covert investigation, federal authorities were able to arrest four Northeast Georgia militia members suspected of planning attacks against government buildings and employees.

Federal Bureau of Investigations agents conducted the investigation into the four suspects since at least last March, and a formal indictment was handed down by a federal grand jury Thursday.

Frederick Thomas, 73, of Cleveland and Emory Dan Roberts, 67, of Toccoa were formally indicted by a grand jury with conspiring to possess an unregistered explosive device and illegally possessing an unregistered silencer.

Ray H. Adams, 65, and Samuel J. Crump, 68, both of Toccoa were indicted on counts of conspiracy to possess and produce a biological toxin and attempted production of a biological toxin.

The FBI is not releasing information regarding the investigation citing that it could harm the prosecution.

Dan Silk, instructor of criminal justice studies at the University of Georgia, said such cases wouldn't necessarily differ from any other type of investigations except that agents probably spent most of their resources collecting evidence against the defendants.

"Maybe you would differentiate it perhaps between a murder — who done it — and that you don't have the suspect from the beginning and the length of the investigation leads up to developing a suspect," Silk said.

An undercover agent, as well as a confidential source, currently out on bond for pending felony state charges, assisted in the investigation, often meeting with the suspects and discussing possible attacks.

Because the FBI was most likely already aware of who the suspects were, they could focus on collecting substantial amounts of evidence to use in the prosecution, Silk said.

"Their efforts from that point on — the length of the investigation is building up sufficient evidence in order to fulfill the probable cause standard for a search warrant and arrest," he said.

Agents were able to obtain a search warrant for each of the four defendants' residences. Those warrants also included authority to search and seize computers located inside the homes, according to an FBI affidavit.

Computer files, even if deleted, can be recovered months or years after they were downloaded, deleted, or viewed on the Internet. Even if deleted, a file still remains on the storage device until it is overwritten.

It hasn't been made public, though, whether evidence was located on seized computers and storage devices.

The biggest obstacle the prosecution must overcome if the case goes to trial, Silk said, is proving the defendants weren't exercising their First Amendment rights guaranteeing freedom of speech.

Silk posed the question, "How do you move beyond a First Amendment protected effort on the suspect's part to express anti-government sentiment, which in and of itself is not illegal?"

In order to prove the defendants weren't simply exercising their rights, the prosecution must prove the men actually intended to commit the acts they are charged with plotting.

"The standard you always hear about is imminent lawless action — whether or not the government can prove that," Silk said.

Imminent lawless action is a term used to define the limits of constitutionally protected speech.

Under the test, speech is not protected by the First Amendment if it's likely to cause violation of the law faster than a law enforcement officer can be reasonably summoned.

"I suspect that's where a lot of the timeline from the FBI's investigation came from — trying to develop enough, because the FBI is keenly aware of First Amendment issues and they want to ensure that they handle those well and with care," Silk said.

According to the affidavit, Thomas and Roberts agreed to purchase weapons and explosives from a dealer to use in attacks on government buildings and employees.

Retired Army Col. Andrew Jurchenko Sr., adjunct professor of ethics and morality at Georgia Military College, said those weapons are easily obtainable.

"If I had $2,000 I could go down to Atlanta to buy a (fully automatic firearm) illegally from a criminal element," Jurchenko said.

"There are a lot of illegal things out there that the underworld deals with and the criminal elements deal with," he added.

Jurchenko said as long as a person knows the right person to deal with, explosives and illegal firearms can be bought on the black market.

"You can go downtown and buy guns. That's not a problem. Explosives? That's not a problem," he said.

Another way weapons are obtained for illegal purposes is by theft, Jurchenko said.

"What I'm talking about is typical stealing from construction sites," he said. "These explosives are used everyday in our country to clear roads, clear forests, for mining, so you could go steal that stuff, as well as buy it from the black market."

After 9/11, explosives manufacturers were required to include tracers in explosives so they can be traced back to the manufacturer and possibly determine who bought the device.

While the FBI hasn't released information about how they became aware of the suspects' alleged plot, Silk said there are a variety of ways to uncover such plans.

"There's a wide spectrum of ways that happens," he said.

"On one end you have truly concerned citizens who happen to overhear something or maybe they spend their time with people that express some views and then one day they hear something that's over the top and they don't want to be involved anymore," Silk added.

In other cases, such as the militia's alleged terror plot, Silk said, a confidential source may come forward in hopes of receiving an incentive for providing information.