Two days into the Democratic National Convention, predictions of mass arrests to keep order in Philadelphia had turned out to be a bust – a few dozen protesters had been issued municipal citations, but none had been taken to jail.

That is until Tuesday night, when four Bernie Sanders supporters scaled the fence around the Wells Fargo Center where Democrats nominated Hillary Clinton as their presidential candidate, entering an off-limits security zone set up by the Secret Service.

Anna Marie Sternberg, one of the four, said she vaulted the fence to protest "the death throes of our democracy." 

"I see the students fighting really hard," said Sternberg, 69, of California, who plans to vote for Green Party candidate Jill Stein. "I came here to support them and stand up for our democracy. We need to get it back." 

But unlike 59 protesters who were briefly detained and fined $50 after being cited for similar activities as the DNC kicked off in Philadelphia this week, Sternberg and three other fence-jumpers were arrested by the Secret Service on misdemeanor charges of entering restricted grounds. The charges could carry up to a year in prison.

Sternberg was arrested around 8:30 p.m. Tuesday along with Barbara Burns, of Boston, Katherine Roberts, of North Carolina, and James Williams, of Maryland. They were detained overnight in the city's federal detention center before all four were released on their own recognizance after a hearing Wednesday afternoon. 

Defense attorney Trevan Borum, who is representing Burns, said the protesters didn't realize they would get treated differently than previous protesters who just got fines.

"I think that her landing in federal court, and the other protesters getting civil citations, was quite a surprise," Borum said of his client.

Philadelphia decriminalized minor offenses several weeks before the convention to lessen the odds of the mass arrests that darkened the 2000 Republican National Convention in Philly.

The city planned to open city prisons in the event of mass arrests, but despite marches by thousands of protesters storming through the city for causes like Sanders' campaign, Black Lives Matter and marijuana legalization, not a single arrest was reported until Tuesday night. 

A spokeswoman for the Philadelphia U.S. Attorney's Office did not respond to requests for comment on why these protesters were arrested instead of cited.

Sternberg's attorney, Paul Hetznecker, said he plans to explore "whether or not they were selectively prosecuted" and why the decision was made to "charge them as opposed to following through on the citation they issued."

Sternberg provided a copy of the citation she first got when city police detained them, gave them citations and told them they would be free in a few hours, before they found out they would face federal charges.

"All of a sudden, we were put in the paddy wagon and taken to the federal jail," she recounted, adding that they had no idea they would later be charged with a federal misdemeanor. "Nobody really told us til after we got there." 

Borum asserted that these protesters were legitimately exercising their First Amendment rights by trying to get in closer proximity to the convention when they climbed the fence.

"What good are First Amendment rights if you're in the middle of a forest protesting? ... They deliberately segregated these protesters so their message couldn’t be heard," Borum said. "They segregated these protesters because the Democratic National Committee wanted to present a charade of party unity even in light of what the committee did to Bernie Sanders. These people have every right in the world to scream about that, because it was entirely unfair."

No court date has yet been set for the protesters.