Many students who participate in the experiment are are preparing for careers in law enforcement.

On a Friday afternoon in April, Texas State University freshman Kendyl Cutshall stopped by a research facility near campus to shoot a police officer for class credit. Inside a simulated classroom building at the Advanced Law Enforcement Rapid Response Training (ALERRT) center near the Central Texas town of San Marcos, she donned protective eyewear as doctoral student Aaron Duron explained the scenario.

"You've committed a crime, and you've run from the police," he said, handing her a modified 9mm Glock pistol that fires marking cartridges filled with blue detergent. "You're thinking that if you shoot the responding officer, you'll go home instead of going to prison. And you've only got one shot."

Cutshall, clad in high-waisted jeans and a Texas State T-shirt, nodded. Duron directed her to stand in a corner of the room and then stepped outside, closing the door and turning off the lights. As Cutshall waited in the darkness, she raised the pistol and held her finger over the trigger.

Suddenly she heard a loud banging sound, the door swung open and the bright beam of a flashlight shone in her eyes. Cutshall squeezed the trigger. The soap-filled projectile missed Sam Stock, a former SWAT officer and a regional manager of training at the center, who returned fire with a blank. Across the hall, research specialist Bill Sandel watched the action on a closed-circuit camera that recorded the scenario for later analysis. "Cease fire!" he yelled, his voice reverberating off the building's metal walls. Duron, who had been waiting in the hallway, stepped back into the room and turned the lights on. Cutshall, her heart pounding, handed the pistol to him and headed back to campus.

In exchange for her time, Cutshall earned credit in her introductory criminal justice class, which requires students to summarize or participate in research studies. She was one of 161 research subjects, most of them undergraduates at Texas State, in this spring's tactical policing experiment at the center, which is affiliated with the university's criminal justice department.

ALERRT is one of a few centers in the country that not only analyzes active-attack events and trains law enforcement to respond to them, but also tests specific policing techniques and incorporates the results in its training protocol, which has been adopted by the FBI and major cities such as Houston and Miami. The tests are important because active-attack response courses tend to be based on the expertise of career SWAT officers - who, having been trained by different police departments, sometimes disagree about which technique is most effective in a given scenario. ALERRT's director of research, Hunter Martaindale, and his colleagues use the scientific method to settle debates over what works better.

This spring's study compared two techniques for entering a dark room where a shooter might be hiding. Martaindale's team ran the scenario 161 times, sending Stock or another ALERRT instructor into the room to engage the person from one of two randomly assigned locations. Afterward, the researchers scrutinized the footage from each encounter, recording whether the officer or the shooter fired first and noting whether and where the officer was hit. If one method of entering the room proves to give officers an edge, it will be incorporated into ALERRT's low-light tactical course.

To run the scenario enough times to produce useful data, Martaindale and his colleagues need a large number of research subjects. But, Martaindale says, "We can't go to a prison and pull a bunch of cop killers in here and have them simulate what they would do if they're caught." And a criminal mind-set isn't necessary for a study that's testing reaction time and accuracy. That's where Texas State, with its nearly 39,000 students, comes in.

Martaindale and Sandel visit criminal justice classes each semester to recruit volunteers. For Cutshall, the experiment sounded more intriguing than the other study, which involved taking an online survey. "It's not every day you get to shoot at a cop in the dark," she says. "The adrenaline - the thrill of it - is fun, because even though you know it's just a setup, you still have your fight-or-flight instincts going. You've still got that rush."

ALERRT was established in 2002, in the wake of the Columbine High School shooting. In addition to training law enforcement officers, it also trains fire and emergency medical services personnel to respond to attacks with police.

Martaindale, Sandel and ALERRT Executive Director Pete Blair have worked with the FBI to analyze every active-attack event since 2000, combing through news articles and police reports to compile information about the shooter, number of casualties, type of weapon used, where the attack took place and how it ended. That data provides useful context for police: For instance, 98.7% of the incidents involved only one gunman. In cases with more than one shooter, the two stuck close together. "That's a good stat for an officer responding to an active shooter to know," says Stock. "Is it going to make them drop their security posture and say, 'OK, I've shot this guy, this is over'? No, but it certainly helps manage the whole situation."

Criminal justice professors regularly work with police departments to help improve the effectiveness of law-enforcement techniques. But Martaindale argues that the criminal justice field remains too theory-driven and that experimental tactical policing research can be a lonely pursuit in the academy. "We go to academic conferences a couple times a year and do a panel based off of our research, and at a conference with 5,000 people in it, we'll have five people in our room," he says.

Police officers are quicker to recognize the value of such potentially lifesaving research. Martaindale and his team present their work at ALERRT's annual conference, where other sessions focus on school safety, tourniquet use and emergency communication among first responders. "We go to our conference," he says, "and we'll have 300 or 400 people in the room because it's information that the officers really want."

Many of the student subjects who are preparing for careers in law enforcement feel the same way, knowing they or their colleagues may one day be on the other side of the scenario. Junior criminal justice major Jacob Parrott says matter-of-factly: "I don't really like shooting even a training round at somebody, but if what I'm doing can help law enforcement potentially save a police officer's life in a real situation down the road, that's worth it."

Brianne Boiarsky, who plans to work for the Department of Homeland Security and took part in this spring's darkened-room experiment, says the exercise helped her channel a shooter's mind-set and anticipate what he or she might do in a real-life situation. "Whenever those lights go off, your defense goes up, and it's almost a different version of yourself," she says, likening it to "high-stakes laser tag."

"It's fun, because you're not getting attacked, except by your own emotions and nervousness and heart-rate increase," she explains. "It's a really exciting experience, and I would do this for extra credit a thousand more times."