Police officers in helmets formed barriers by stretching orange netting across intersections. Hordes of bicyclists participated in rolling protests through nighttime streets, and helicopters hovered overhead.
These tableaus and others were described as they happened in text messages that spread from mobile phone to mobile phone in New York City and beyond. The people sending and receiving the messages were using technology, developed by an anonymous group of artists and activists called the Institute for Applied Autonomy, that allowed users to form networks and transmit messages to hundreds or thousands of telephones.
Although the service, called TXTmob, was widely used by demonstrators, reporters, and possibly even police officers, little was known about its inventors. Last month, however, the New York City Law Department issued a subpoena to Tad Hirsch, a doctoral candidate at the Massachusetts Institute of Technology who wrote the code that created TXTmob.
Lawyers representing the city in lawsuits filed by hundreds of people arrested during the convention asked Hirsch to hand over voluminous records revealing the content of messages exchanged on his service and identifying people who sent and received messages. Hirsch says that some of the subpoenaed material no longer exists and that he believes he has the right to keep other information secret.
"There's a principle at stake here," he said recently by telephone. "I think I have a moral responsibility to the people who use my service to protect their privacy."
The subpoena, which was issued February 4, instructed Hirsch, who is completing his dissertation at MIT, to produce a wide range of material, including all text messages sent via TXTmob during the convention, the date and time of the messages, information about people who sent and received messages, and lists of people who used the service.
In a letter to the Law Department, David B. Rankin, a lawyer for Hirsch, called the subpoena "vague" and "overbroad," and wrote that seeking information about TXTmob users who have nothing to do with lawsuits against the city would violate their First Amendment and privacy rights.
Lawyers for the city declined to comment.
The subpoena is connected to a group of 62 lawsuits against the city that stem from arrests during the convention and have been consolidated in Federal District Court in Manhattan. About 1,800 people were arrested and charged, but 90 percent of them ultimately walked away from court without pleading guilty or being convicted.
Many people complained that they were arrested unjustly, and a State Supreme Court justice chastised the city after hundreds of people were held by the police for more than 24 hours without a hearing.
The police commissioner, Raymond W. Kelly, has called the convention a success for his department, which he credited with preventing major disruptions during a turbulent week. He has countered complaints about police tactics by saying that nearly a million people peacefully expressed their political opinions, while the convention and the city functioned smoothly.
Hirsch said the idea for TXTmob evolved from conversations about how police departments were adopting strategies to counter large-scale marches that converged at a single spot.
While preparing for the 2004 political conventions in New York and Boston, some demonstrators decided to plan decentralized protests in which small, mobile groups held rallies and roamed the streets.
"The idea was to create a very dynamic, fluid environment," Hirsch said. "We wanted to transform areas around the entire city into theaters of dissent."
Organizers wanted to enable people in different areas to spread word of what they were seeing in each spot and to coordinate their movements. Hirsch said that he wrote the TXTmob code over about two weeks. After a trial run in Boston during the Democratic National Convention, the service was in wide use during the Republican convention in New York. Hundreds of people went to the TXTmob Web site and joined user groups at no charge.
As a result, when members of the War Resisters League were arrested after starting to march up Broadway, or when Republican delegates attended a performance of The Lion King on West 42nd Street, a server under a desk in Cambridge, Mass., transmitted messages detailing the action, often while scenes on the streets were still unfolding.
Messages were exchanged by self-organized first-aid volunteers, demonstrators urging each other on, and even by people in far-flung cities who simply wanted to trade thoughts or opinions with those on the streets of New York. Reporters began monitoring the messages too, looking for word of breaking news and rushing to spots where mass arrests were said to be taking place.
And Hirsch said he thought it likely that police officers were among those receiving TXTmob messages on their phones.
It is difficult to know for sure who received messages, but an examination of police surveillance documents prepared in 2003 and 2004, and unsealed by a federal magistrate last year, makes it clear that the authorities were aware of TXTmob at least a month before the Republican convention began.
A document marked "NYPD SECRET" and dated July 26, 2004, included the address of the TXTmob Web site and stated, "It is anticipated that text messaging is one of several different communications systems that will be utilized to organize the upcoming RNC protests."
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