AKRON, Ohio — A federal jury took less than 90 minutes to convict a 24-year-old Cleveland man of plotting with fellow anarchists to blow up a bridge spanning the Cuyahoga Valley National Park.

Jurors found Joshua Stafford guilty on all three counts: conspiracy to use a weapon of mass destruction, attempting to use a weapon of mass destruction, and maliciously attempting to destroy the Ohio 82 bridge with a weapon of mass destruction.

He could face a life prison term for the foiled plot, though his four co-conspirators, who pleaded guilty rather than go to trial, received prison terms ranging from six to 11 ½ years. U.S. District Judge David Dowd Jr. scheduled sentencing for Sept. 11.

Joshua Stafford, 24, of Cleveland, is scheduled to be sentenced Sept. 11.

The verdict came after 2 ½ days of testimony from an FBI informant who sold the conspirators fake bombs and plastic explosives, and from Stafford, who took the witness stand while also acting as his own lawyer and posed questions to himself.

Dowd had ordered Stafford to write down his questions and answers, sit in the witness stand and dictate the exchange to the jury.

"Question," Stafford said. "So at any time did you have complete knowledge that a destructive incident was supposed to happen that day?

"Answer: No I did not.

"Why? Because I didn’t think Douglas Wright was capable of doing such things."

Stafford said Wright, the group’s ringleader, often boasted of wanting to take the peaceful Occupy Cleveland movement in a violent direction, but never believed Wright would be able to obtain explosives.

An undercover FBI agent sold the group two phony bombs and fake C4 plastic explosives, and an FBI informant drove the five men to the base of the bridge on the night of April 30, 2012 to plant the explosives. The men were arrested the same night after attempting to detonate the phony explosives with a cell phone.

During closing arguments Thursday, Stafford spoke for about 40 minutes, periodically losing his train of thought.

He told the jury he went along with the group because the FBI informant had promised to buy him a pack of cigarettes and dinner at Applebee’s.

Stafford said he was not present for any of the group’s planning meetings, and was unaware his friends intended to blow up the bridge.

"I didn’t know that anything serious was going to happen," Stafford said. "I thought, at the most, we were going to stencil or spray paint the bridge" with graffiti. "I just wanted to do some painting action, to put some art up."

Assistant U.S. Attorney Duncan Brown challenged Stafford’s claims of innocence. He reminded the jury that Douglas Wright had introduced Stafford as "someone they could trust, a dude who likes to do crazy ... revolutionary" stuff.

Brown cast doubt on Stafford’s contention that he thought the group intended to tag the bridge with spray painted anti-government messages — not blow it up. He noted that Stafford placed a lunch box containing the phony bomb and C4 plastic explosives at the base of the bridge, and punched in the four-digit code on a cell phone he expected would detonate the bomb.

Brown also took issue with Stafford’s claims he was a peaceful person, citing two incidents when Stafford was a juvenile inmate and attacked guards. Stafford explained that both attacks were in self-defense.

One of the guards received "permanent brain damage" and the other was slashed with a sharp implement, Stafford said.

"Do you consider yourself an anarchist?" Brown asked.

"To the extent of not agreeing with the government, yes," Stafford responded.

Stafford was the only one from the group to stand trial. Dowd determined the other four gang members were domestic terrorists and sentenced them all to prison after they pleaded guilty to charges related to the bombing plot.

Wright, 27, of Indianapolis, is serving 11 1/2 years in prison; Brandon Baxter, 21, of Lakewood, is serving a sentence of nine years and nine months; Connor Stevens, 21, of Berea, received an eight-year sentence; and Anthony Hayne, 35, of Cleveland, was sentenced to six years.

In a statement released after the verdict, U.S. Attorney Steve Dettelbach credited the FBI with saving lives.

"By being diligent, smart and responsible, law enforcement agents were able to not only literally defuse a dangerous situation, but they also were able to catch a dangerous group of violent men before they were able to harm anyone else," Dettelbach said.

Stephen Anthony, special agent in charge of the FBI’s Cleveland office, said Stafford was a key member of the conspiracy.

"This defendant’s callous disregard for our community, all in the name of making his own ideological views known, reinforces the need for law enforcement to work diligently to confront and stop terrorists from committing violent acts against our fellow citizens," Anthony said.