Say you're traveling on an airplane and you notice some other passengers behaving in a suspicious manner -- acting nervous, looking around furtively, conferring in a language you don't understand and a manner you find frightening.
Under a new federal law, you can report your concerns to the crew without fear of being sued by the subjects of your complaint, even if the suspicions turn out to be unfounded.
The little-noticed "good faith" law was passed by Congress on July 27 as part of a sweeping homeland security bill implementing recommendations of the 9/11 Commission.
The measure gives immunity to any "John Doe" whistle-blower who reports possible terrorist activity or other worrisome behavior by fellow passengers on planes, trains, cruise ships and buses, based on "objectively reasonable suspicion" that is not defined.
Its purpose is to protect average citizens from civil liability that otherwise might arise from speaking up when they fear public safety is at stake, and also to shield officials who take "reasonable action in good faith to respond to such activity."
The law does not protect individuals who knowingly make false statements. That hasn't allayed objections by the American Civil Liberties Union, which warns that the provision could encourage racial and religious profiling of innocent travelers who happen to look or talk differently from their skittish seat mates.
The measure was made retroactive to Sept. 1, 2006, specifically to negate a lawsuit filed by six Muslim clerics against unnamed passengers who complained about them.
The imams were removed from a US Airways flight from Minneapolis to Phoenix after other travelers were unnerved by their prayers in the terminal, their seating patterns, requests for seat belt extenders and other things.
The clerics, who had been headed to a meeting of the North American Imams Federation, were handcuffed, searched and detained by airport police, then later were found to pose no danger. Their lawsuit against the airport and airline is ongoing, but the "John Doe" targets were dropped.
The "good faith" amendment was co-written by Sen. Susan Collins, R-Maine, and Sen. Joseph Lieberman, I-Conn.
One impetus they cited was the May arrests of six men charged with conspiring to murder American soldiers at Fort Dix, N.J.
A clerk at a nearby Circuit City store had called local police, saying one of the men had tried to duplicate a "disturbing" video. It allegedly showed men firing automatic weapons and shouting in Arabic, reminding the clerk of the 9/11 terrorists.
And two weeks ago, the FBI released photos of two men whose images were snapped by a crew member of a Washington State Ferry boat.
The men had raised the crew member's suspicions on several rides by asking questions about structural details and entering areas of the boats that are off-limits. The FBI is trying to identify them.
Muslim groups have protested that the photos' release is a form of profiling because the men could be perceived as Middle Eastern.
In arguing for the law in the Senate, Sen. Collins said the average person must feel free to speak up.
"An alert citizenry is one of our best defenses against terrorist attacks," she said. "That is why the New York subway system has signs reading, 'If you see something, say something.'"
U.S. Rep. Bill Schuster, R-Hollidaysburg, who co-sponsored the measure in the House, said, "No American should be forced to second-guess a decision to alert authorities that could save the lives of others."
"The Fort Dix incident reminds us that ordinary people can and do play an important role in the security of our communities," added Sen. Lieberman. "This bill will encourage others to be alert to suspicious activities ... without fear of repercussions."
Sally Kalson can be reached at firstname.lastname@example.org or 412-263-1610.