He said police have a history of abusing such tactics, sometimes infiltrating purely peaceful protest groups to search for troublemakers.
But if the allegations are true, police were justified in moving quickly to take the men off the streets, even if the terrorism charges don't stick.
Just one week before their arrest, at least two of the suspects were involved in a minor confrontation with police captured on a video that was then posted on YouTube and aired widely by Chicago media, said another defense attorney, Sarah Gelsomino.
The men had been stopped by police after turning their car into a private driveway.
In the video, one officer asks another what Chicago police would have said in 1968 when they clashed with demonstrators at the Democratic National convention.
"Billy club to the ... skull," the officer responds. Another officer says to the men in the car, who the police take as protesters, "We'll come look for you."
Documents filed by prosecutors in support of the charges in Chicago painted an ominous portrait of the men, saying the trio also discussed using swords, hunting bows and knives with brass-knuckle handles in their attacks.
Relatives and acquaintances painted a starkly different picture.
Activist Bill Vassilakis, who said he let the men stay in his apartment, described Betterly as an industrial electrician who had volunteered to help with wiring at The Plant, a former meatpacking facility that has been turned into a food incubator with the city's backing.
"All I can say about that is, if you knew Brent, you would find that to be the most ridiculous thing you've ever heard. He was the most stand-up guy that was staying with me. He and the other guys had done nothing but volunteer their time and energy," he said.
Betterly appears to have a history of minor run-ins with law enforcement.
Earlier this year, he was cited for disorderly intoxication in February in Miami-Dade County, Fla., but the case has been dismissed, according to online court records.
Authorities in Oakland Park, Fla., said Betterly and two other young men walked into a public high school last fall after a night of tequila drinking and took a swim in the pool, according to a report in the South Florida Sun-Sentinel.
They stole fire extinguishers from three school buses, discharged one and smashed a cafeteria window with another. The vandalism caused about $2,000 in damage. Betterly was charged with burglary, theft and criminal mischief, the newspaper said.
Chase grew up in Keene, N.H., and moved to Boston a few years ago before becoming active in the Occupy movement, said his aunt, Barbara Chase of Westmoreland, N.H.
Jared Chase's father, Steve Chase, died about five weeks ago after a long struggle with a disease that left him disabled, Barbara Chase said. The family had been waiting for him to come home before having a funeral.
She said she was stunned to learn of the charges against her nephew.
"That surprised me because he's not that dumb," said Barbara Chase. "He always seemed harmless, but who knows? Outside influences sometimes can sway people to do things that they normally wouldn't do."
Elsewhere around Chicago, demonstrations remained relatively small. Scattered groups of protesters gathered in some neighborhoods, including several hundred who marched to the mayor's house.
Late in the day, another group gathered in the Loop business district and marched down the city's famous Michigan Avenue. Police on horseback and bicycle kept them away from diners at outdoor cafes who ventured downtown despite wide-ranging security precautions.
The largest protests were expected Sunday, when thousands of people were expected to march from a band shell on Lake Michigan to the McCormick Place convention center, where NATO delegates will meet.
Associated Press writers Jason Keyser, Jim Suhr, Tammy Webber and Nomaan Merchant also contributed to this report.
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