In the three years since the mass shooting in a Colorado movie theater that left 12 people dead and 70 injured, theater owners have largely resisted pressure to increase security at their venues. But this week’s massacre at a Lafayette cineplex has reignited the debate about whether movie chains, which have emerged as ripe targets for lone shooters, should take steps to better screen and protect patrons.

In addition, the industry has become increasingly vulnerable to legal challenges that claim they share responsibility for the violence.

Critics say practical security measures targeting weapons are required to stop the next attack.

“Nothing has been done,” said Aaron Cohen, a Los Angeles-based counterterrorism expert who trains police forces around the U.S.

Cohen says the lack of urgency is due to the relative low number of attacks at these venues and the expense required for added security personnel and technology. He says that had there been security measures in place at The Grand 16 in Lafayette where Thursday’s attacks took place, the odds of such an incident occurring would have been lowered substantially.

“If they don’t put those protocols in movie theaters, they’re going to keep getting hit,” he said.

Lafayette Police Chief Jim Craft said The Grand 16 employs security guards just for Friday and Saturday nights. There were none on site Thursday. He called the lack of security a “big concern.” George Solomon, owner of New Orleans-based parent company Southern Theatres, did not return calls Friday seeking comment.

Following the 2012 massacre in Aurora, Colorado, the Cinemark movie chain was hit with at least 20 lawsuits from victims and their families alleging that the company was negligent in failing to provide adequate security at the Aurora location. Two of those civil cases are headed for trial next year.

Plaintiff attorneys claim that the company failed to take prior threats seriously and did not have adequate security personnel or technology. One lawsuit claims that local police received 100 emergency calls from the theater in the months leading up to the shooting. In a filing, Cinemark denies such claims, saying that the massacre “was legally unforeseeable.”

Denver attorney Christina Habas, who represents 18 of the families, disagrees. She says the natural characteristics of the movie-going experience — a dark room, a large group of strangers, and the distraction of a big screen — “makes people in a movie theater the softest of soft targets,” a reality that theater owners have not taken seriously. “When you have a business and you’re inviting people there, you need to think about how vulnerable they are,” she said.

The Colorado lawsuits are alleging Cinemark violated the state’s Premises Liability Act, which covers so-called “slip-and-fall” accidents protecting people from harmful incidents perpetrated by a third party on the premises of a private business. Louisiana has a similar statute, but New Orleans lawyer David Melancon, whose firm concentrates in premises liability, says victims also are protected under provisions in the state’s civil code.

In these cases, plaintiffs have the burden to prove what is foreseeable and what is not, which can often “get a little touchy-feely because that standard may be applied differently by different jurisdictions.”

“It’s a challenging standard from the plaintiff’s perspective, but certainly not insurmountable,” he said.

As gun violence by lone shooters becomes more common, Gabriel Chin, a law professor at the University of California at Davis, said “you’re more likely to see lawsuits in cases like this.” And that is incentivizing companies and organizations like universities and municipalities to put practices in place to minimize safety risks. They can be as simple as providing parking lots with better lighting to prevent assaults or increasing the presence of security cameras.

“There’s no question, whether it’s malls or movie theaters or sports stadiums, when people get together in significant numbers, (owners) are going to have to take threats seriously and they’re going to have to take reasonable care to protect their patrons,” Chin said.

Theater chains that are privately owned are not forced to make changes. The National Association of Theatre Owners, a trade group in Washington that represents more than 30,000 movie screens in the U.S., did not respond to a request for comment. After the Aurora shooting, the organization released a statement that said it would “review security procedures” but offered no specifics.

Despite the widespread alarm, many think that expecting private businesses like movie theaters to provide security is an overreach.

“If Congress or other legislative bodies mandate the installation of metal detectors or other kinds of security enhancements for movie theaters, what happens if the next incident is at an auto mall? Will they require similar measures there?” asked Frank Scafidi, a spokesperson for the National Insurance Crime Bureau, a nonprofit group in Sacramento. “We can’t harden every public place in America on the theory that we’re preventing some future tragedy.”

So far, the movie-going public is slowing. Motion Picture Association of America data shows that both tickets sold (1.27 billion) and average tickets sold per person (3.7) declined 6 percent in 2014 from the previous year.