Takoma Park, Maryland - To friends in the protest movement, Lucy was an eager 20-something who attended their events and sent encouraging e-mails to support their causes.

    Only one thing seemed strange.

    "At one demonstration, I remember her showing up with a laptop computer and typing away," said Mike Stark, who helped lead the anti-death-penalty march in Baltimore that day. "We all thought that was odd."

    Not really. The woman was an undercover Maryland State Police trooper who between 2005 and 2007 infiltrated more than two dozen rallies and meetings of nonviolent groups.

    Maryland officials now concede that, based on information gathered by "Lucy" and others, state police wrongly listed at least 53 Americans as terrorists in a criminal intelligence database - and shared some information about them with half a dozen state and federal agencies, including the National Security Agency.

    Among those labeled as terrorists: two Catholic nuns, a former Democratic congressional candidate, a lifelong pacifist and a registered lobbyist. One suspect's file warned that she was "involved in puppet making and allows anarchists to utilize her property for meetings."

    "There wasn't a scintilla of illegal activity" going on, said David Rocah, an attorney for the American Civil Liberties Union, which filed a lawsuit and in July obtained the first surveillance files. State police have released other heavily redacted documents.

    Investigators, the files show, targeted groups that advocated against abortion, global warming, nuclear arms, military recruiting in high schools and biodefense research, among other issues.

    "It was unconscionable conduct," said Democratic state Sen. Brian Frosh, who is backing legislation to ban similar spying in Maryland unless the police superintendent can document a "reasonable, articulable suspicion" of criminal activity.

    The case is the latest to emerge since the Sept. 11 attacks spurred a sharp increase in state and federal surveillance of Americans. Critics say such investigations violate constitutional guarantees of freedom of speech and assembly, and serve to inhibit lawful dissent.

    In the largest known effort, the Pentagon monitored at least 186 lawful protests and meetings - including church services and silent vigils - in California and other states.

    The military also compiled more than 2,800 reports on Americans in a database of supposed terrorist threats. That program, known as TALON, was ordered closed in 2007 after it was exposed in news reports.

    The Maryland operation also has ended, but critics still question why police spent hundreds of hours spying on Quakers and other peace groups in a state that reported more than 36,000 violent crimes last year.

    Stephen Sachs, a former state attorney general, investigated the scandal for Gov. Martin O'Malley - a Democrat elected in 2006. He concluded that state police had violated federal regulations and "significantly overreached."

    According to Sachs' 93-page report and other documents, state police launched the operation in March 2005 out of concern that the planned execution of a convicted murderer might lead to violent protests.

    They sent Lucy to join local activists at Takoma Park's Electrik Maid, a funky community center popular with punk rockers and slam poets. Ten people attended the gathering, including a local representative from Amnesty International.

    "The meeting was primarily concerned with getting people to put up fliers and getting information out to local businesses and churches about the upcoming events," the undercover officer reported later. "No other pertinent intelligence information was obtained."

    That proved true for all 29 meetings, rallies and protests that Lucy ultimately attended. Most drew only a handful of people, and none involved illegal or disruptive actions.

    Using the aliases Lucy Shoup and Lucy McDonald, she befriended activists. "I want to get involved in different causes," she wrote in an e-mail, citing her interest in "anti-death penalty, antiwar and pro-animal actions!!!"

    Max Obuszewski, a Baltimore pacifist who leads antiwar protests, said Lucy asked about civil disobedience, but didn't instigate any. "She never volunteered to do anything, not even hand out leaflets," he said. "She was not an agent provocateur."

    Greg Shipley, a state police spokesman, said that no one in the department had been disciplined in connection with the spying program. Lucy, who has not been publicly identified, would not consent to an interview, he said.

    The surveillance, Shipley said, was inappropriate. And the listing of lawful activity as terrorism "shouldn't have happened, and has been corrected."

    Most of the files list terrorism as a "primary crime" and a "secondary crime," then add subgroups for designations such as antiwar protester.

    Some contain errors and inconsistencies that are almost comical.

    Nancy Kricorian, 48, a novelist on the terrorist list, is coordinator for the New York City chapter of CodePink, an antiwar group. She serves as liaison with local police for group protests, and has never been arrested.

    "I have no idea why I made the list," she said. "I've never been to the state of Maryland, except maybe to stop for gas on the way to Washington."

    Josh Tulkin, 27, a registered lobbyist with the Virginia state Legislature, is cited under "terrorism - environmental extremists." Tulkin was deputy director of Chesapeake Climate Action Network, an environmental group that claims 15,000 members and regularly meets with governors and members of Congress.

    "If asking your elected officials a question about public policy is a crime, then I'm guilty," he said.

    Barry Kissin, 57, a lawyer who ran unsuccessfully for Congress in 2006, heads the Frederick Progressive Action Coalition, a group that works "for social, economic and environmental justice," according to his police file. Their protests "are always peaceful," it added.

    He was labeled "Terrorism - Anti-Government."

    Nadine Bloch, 47, runs workshops for protest groups that seek corporate responsibility and builds huge papier-mache puppets often used in street marches. Her terrorism file indicates she participated in a Taking Action for Animals conference in Washington on July 16-18, 2005.

    Animal rights, Bloch said, is one of the few causes she doesn't actively embrace. Besides, she was attending an educators conference in Hawaii that week as a contractor for the National Oceanic and Atmospheric Administration.

    "This whole thing," she said, "is so absurd."