Left unattended, no accessory looks as menacing these days as a backpack.
At the airport. On the subway. At a sports event.
And, as a result of the two backpack-encased bombs that exploded near the finish line at the Boston Marathon, sports teams and leagues around the world are rethinking what kind of bags, satchels, purses and, yes, black nylon backpacks should be allowed inside stadiums and arenas.
The packs will even be the focal point of a conference this summer of stadium-security personnel in Orlando .
"After what happened ... I wouldn't be surprised if the number of people eliminating backpacks would increase," said Lou Marciani, director of the National Center for Spectator Sports Safety and Security, founded in 2006 and based at the University of Southern Mississippi in Hattiesburg.
Next Saturday, more than 165,000 people are expected at Churchill Downs for the Kentucky Derby. Backpacks, duffel bags and large purses have been banned from the track since 2002 — part of the clamp-down that followed the Sept. 11 attacks. Still, Derby officials have told fans their bags will undergo increased security checks for this year's race.
No matter where the world ends up on the bag-check spectrum, some fans may never again regard the pack slung across their body quite the same way.
"I never really thought about backpacks until last week, and now you notice backpacks all over the place," said Ryan Hershberger of Hartwell, Ga., as he headed into a Colorado Rockies game carrying a black backpack. "It makes you think."
Down the street, at the Denver Nuggets game, a handful of fans shared the same sentiment.
"I've been thinking about it all day," Joel Cross said on the concourse at the Pepsi Center in Denver. He and his wife traveled from Harrisburg, Neb., to attend Tuesday night's Nuggets playoff game. "We're from a community where our whole county only has 600 people in it. Nobody is going to bomb us because there's no one there. But we're coming to a populated area."
The NFL beefed up security for thousands of fans attending its annual draft, which runs through Saturday, with metal detectors, pat-downs and about 20 percent more personnel in place than previous years. Backpacks are banned. The league said it would consider what, if any, changes might be made for the 2013 season, which ends with the Super Bowl in New York next February.
Major League Baseball's security officials met Thursday but Commissioner Bud Selig said no changes are expected in the rules on bags fans can bring to ballparks, generally limited to 16x16x8 inches. The meeting was scheduled before the Boston explosions that killed three and injured more than 260/
"I wouldn't say that Boston has changed anything," Selig said. "Each club makes its own decision."
At Yankee Stadium, for example, briefcases, coolers and other hard-sided bags or containers are not permitted. At Kansas City's Kauffman Stadium, wrapped presents are banned along with cameras with lenses of 12 or more inches. The Baltimore Orioles ban bags with wheels at Camden Yards.
Boston and San Francisco were among the teams opting to use metal-detecting wands on fans and their possessions this week.
"We've added people, and people are getting in faster now, so we're going to stick with the plan," Giants president and CEO Larry Baer said.
Though the marathon bombings caught the attention of the world, not every event or championship, especially overseas, is beefing up or changing security measures.
For instance, officials at Manchester United, the FA Cup final and the European Champions League say their policies, which either ban large bags or strongly discourage them, are under constant review but not set to change.
"We did, of course, contact the police in the aftermath of the Boston bombings, as part of our commitment to the security of fans and visitors to the stadium," Manchester United said in a statement.
At Wimbledon, where tennis action starts in June, no changes are planned.
"It was a terrible event, but we have no reason to believe it's something that has a direct impact on Wimbledon," All-England Club chief executive Richard Lewis said, referring to the Boston explosions.
At the Summer Olympics in London, soft-sided bags were required to fit under seats and couldn't hold more than 25 liters (6 gallons).
Sebastian Coe, who led London's organizing committee, says a ban on backpacks at sports events would not be justified.
"We have to make some pretty tough decisions in the way we want to live our lives," he said. "It's very easy to draw all sorts of conclusions (from the Boston bombings). Do we want to live in a world where people can't wear backpacks to sporting events? I'm not sure we do."
Organizers in Brazil aren't making any radical changes to their backpack policy for the upcoming Confederations Cup or next year's World Cup. So far, the extensive list of prohibited items includes "unwieldy" bags — no more than 10x10x10 inches and too big to fit under a seat.
Officials in Russia, which hosts the 2018 World Cup, said that whenever a sports-related tragedy occurs, they review what happened "to ensure that our own regulations and procedures are sufficiently covering such potential tragedies or risks."
In Sochi, Russia, site of February's Winter Olympics, security for test events was so stringent that the president of the international skiing federation, Gian Franco Kasper, cracked, "The only moment they didn't inspect our athletes was during the race."
International Olympic Committee member Dick Pound of Canada said one strategy might be to push back security boundaries.
"I remember in Vancouver and other places, the tension between the organizers and the events and the security folks was over the size of the perimeter," Pound said. "If you can move the perimeter back 50 or 100 meters, a backpack bomb is going to have less lethal effect."
In the U.S., NBA spokesman Tim Frank wouldn't comment on specific security practices, beyond saying: "We regularly practice a wide range of state of the art security measures in all of our arenas." The Nuggets have long used wands and searched bags. But Cross' wife, Shelly, said she noticed a more extensive security presence at Tuesday's game than the last time they made the trip to Denver.
"We were here not too long ago and we don't remember this," she said.
At least one backpack developer said she was unaware of any pending changes to basic designs. She also thought the bombings were unlikely to create a need for see-thru or clear backpacks.
"I don't think people want to share their belongings with everyone. Everyone wants their privacy," said Annelies Mertens, a member of the Samsonite development team in Belgium. "I don't think this will have an influence on the way backpacks are made. I don't see that happening."
While the Boston Marathon presented its own set of difficult challenges — securing a 26-mile course dotted with trash cans and spectators on almost every block — one expert says there's no such thing as perfect security guidelines, regardless of venue.
"A no-backpack policy is fine if it applies to everyone," said Derek Catsam, an associate professor at University of Texas of the Permian Basin in Odessa who has studied the safety issue in stadiums. "But then you start making exceptions for people with kids, and for the elderly and for women with purses and people in expensive seats. Where does it end? You can have a policy or not have a policy. But once you start selectively enforcing it, that's going to be problematic."
After the bombings, the NHL's Boston Bruins added metal-detecting wands to their security regimen and checked cars parking in a garage underneath the arena. Security measures vary by arena in the NHL. The New York Islanders, for example, don't allow backpacks; the Detroit Red Wings ban oversized bags and search all bags that are allowed in.
Catsam said security can always be ratcheted up, but then comes the issue of how much convenience people are willing to give up for the sake of safety.
"They could start saying you can bring whatever kind of backpack you want but you have to go through an X-ray system like you do at the airport," he said. "It would take forever and we'd adjust, but I'm not sure what we'll discover or if we'll be making anything really safer."
Marciani, on the other hand, envisions a day when backpacks are as obsolete at a stadium as the bulky transistor radios that fans once brought along so they could listen to play-by-play as they watched the game.
"I think it's just one less aggravation we'd have to put up with," he said. "I'd just say, 'Why backpacks at a stadium?' I don't think we need them."
AP Sports Writers Pat Graham in Denver, Howard Fendrich in Washington, Stephen Wilson, Rob Harris, Steve Douglas and Chris Lehourites in London, Tales Azzoni in Sao Paolo, Brazil, Janie McCauley in San Francisco, Jon Krawczynski in Minneapolis, Graham Dunbar in Geneva, Jimmy Golen in Boston, Ben Walker and Ron Blum in New York, David Ginsburg in Baltimore and Bernie Wilson in San Diego and Associated Press reporter Peter Banda contributed to this report.