Editor's Note: (Danny Cevallos is a CNN legal analyst and an attorney practicing in the areas of personal injury, wrongful conviction and criminal defense in New York, Pennsylvania and the US Virgin Islands. Follow him on Twitter @CevallosLaw. The opinions expressed in this commentary are his. )
(CNN) As of Tuesday evening, 22 people -- including children -- are dead after an explosion outside an Ariana Grande concert at the Manchester Arena in England.
Concerts and sporting events are particularly vulnerable terrorism targets because they feature large, captive audiences and stage high-profile events. With that in mind, what is the scope of responsibility of a stadium owner to paying eventgoers?
Our law is derived from English common law, and a feudal system historically designed to protect landowners' proprietary interests. Back then, the landowner was considered a sovereign within the boundaries of his property, and the only duty he owed people on the property was to try not to willfully or wantonly injure them.
Modern law in both countries has evolved significantly. In the United States, the duty owed by owners and possessors of land has come to depend on the status of the person injured there: an invitee, licensee or trespasser. Concertgoers would be classified as "invitees": people on the property for a business purpose. A stadium in the United States owes an invitee the duty to keep the premises in a reasonably safe condition from foreseeable harm, or to warn invitees of hidden or concealed dangers.
A classic example of fulfilling this duty is the netting in a baseball stadium in the areas where foul balls are frequently hit. Getting struck by a foul ball is a foreseeable injury to a baseball fan sitting in that area, with a relatively inexpensive solution.
It's also a very tangible example of where to draw the line when it comes to foreseeable injury. You may have noticed that the foul ball netting doesn't extend to cover every seat at the ballpark -- just the areas where foul balls are considered especially dangerous. Of course, technically, balls can be hit anywhere in a stadium, but the decision not to net every seat weighs the likelihood of harm against the cost of protection -- with the result that those fans in the nosebleed seats are on their own.
Criminal activity, which includes terrorism, is different. It's impossible for any stadium owner to completely eliminate the risk of criminal activity by a third party. The law reflects this understanding; a premises owner generally has no duty to protect invitees from criminal acts by third parties. There's an exception: a premises owner must use ordinary care to protect people from criminal acts of third parties, if he knows or has reason to know of an unreasonable and foreseeable risk of harm.
That's the thing though: Acts of terror don't happen often, but in a post 9/11 society, they are all "foreseeable" -- even if they have never occurred at a particular venue. In fact, that's what makes terrorism effective: One horrific attack at a concert can change the way we all attend these events.
For example, one of the lasting effects of the events of 9/11 is that terrorism is now forever foreseeable at American airports, and other events or transportation where large numbers of people congregate. Even when terror attempts are discovered and foiled by the authorities, the close call itself is as burned into our collective "foreseeability" as if the attack had been successful. The thwarted "shoe bomb" years ago and the "laptop" threat today are examples of threats that may never materialize, but are "foreseeable" in that we can easily imagine the horror of it happening.
Security measures have already changed a lot at stadiums in the years since 9/11. If our bags were checked prior to that, it was usually for booze; now it's for explosives. Now we are routinely patted down or wanded. After Manchester, the definition of reasonable security measures may be forever altered, and the standard might be raised, not just by stadium owners seeking to allocate risk, but by international standards.
Perhaps TSA-style screening is the new future of concerts and sporting events.
This is yet another reason why terrorism is so insidious: The harms extend far beyond any blast radius, by redefining "foreseeable" harm for the rest of us.