“What we found in both cities was that the police response to reports of gunfire seemed to have improved following the installation of ShotSpotter,” Piza told Undark.

Stun gun vs Taser

Complications related to the brain or nervous system are rare, but do occur, including loss of consciousness, seizures, abnormal brain activity and confusion. This is more likely to occur if a subject is shot at a close distance or directly to the head, which is not usually the case since those are not the recommended targets. The probability of causing a seizure is very low.

He added that in both cities, districts that used ShotSpotter saw increases in the collection of ballistic evidence and the recovery of illegal firearms. And while the police in both cities also spent more response time at ShotSpotter locations as opposed to 911 calls, none of this activity led to a reduction in crime.

That report was not peer reviewed, but two others that were have appeared this year focusing on the ShotSpotter programs in Chicago and Kansas City, both of which launched their programs in 2012.

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The widespread use of ECDs, with more than a 1,070 estimated worldwide uses per day, as reported by TASER manufacturer Axon, has led many to wonder: What happens to the human body after being tased?

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Rod McCullom is a Chicago-based science journalist and senior contributor to Undark whose work has been published by Scientific American, Nature, The Atlantic, and MIT Technology Review, among other publications.

Other cities, including Houston — the nation’s fourth-largest city — are rethinking the merits of gunfire detection. John Whitmire, the city’s mayor, recently described the technology as a “gimmick” with no impact on the city’s serious gun violence epidemic, according to ABC 13 Houston. The news station found that only 5 percent of ShotSpotter notifications over nearly two years led to an arrest.

The Kansas City research, which was also led by Piza and published in Criminology & Public Policy, examined about 11,500 gunfire events located by sensors in Kansas City through the end of 2019.

An ampere, or amp, is the unit used to measure current. A small current -- 200 microamps –- applied directly to the heart can cause a fatal rhythm called ventricular fibrillation.

While the police in both Chicago and Kansas City spent more response time at ShotSpotter locations as opposed to 911 calls, none of this activity led to a reduction in crime.

The taser delivers 19 short pulses per second over 5 seconds, with an average current of 2 milliamps, according to TASER manufacturer Axon. It creates an electric field, which stimulates nerve cells called alpha motor neurons to send an electrical impulse. The impulse travels to muscles and causes short, sustained muscle contractions.

“At the end of the day we can’t say with great confidence that there were shootings that were prevented as a result of the ShotSpotter installation,” said Philip Cook, a Duke University economist and criminologist, and author of the study. Even so, he added, “The possibility of taking a minute or two off the response time would mean the difference between life and death for a victim who’s bleeding out on the scene.”

The Chicago study, which analyzed about 85,500 gunfire events between January 2008 and December 2019, was led by Eric Piza, a professor of criminology and criminal justice at Northeastern University. It is believed to be part of the largest research project on gunfire detection technology to date. The researchers wanted to determine the impact of gunfire locators on officers’ responses and searches, ballistic, and evidence collection, and on gun violence and crime overall.

Pocket taser

The taser has two modes: the first, pulse mode, causes neuromuscular incapacitation as the neural signals that control muscles become uncoordinated, and muscles contract at random. The second mode, drive-stun, uses pain to get compliance.

Cleveland recently expanded the technology across the entire city, but other cities like Seattle, Washington and Dayton, Ohio have abandoned their programs.

Researchers and policy analysts like Clemmons emphasize that policing technologies cannot work in a vacuum. “Whether it’s body-worn cameras, CCTV, or an Apple Watch tracking your heart rate, changes in policies, procedures, and — most importantly — practices must accompany any tool in order for it to make a meaningful difference,” she wrote in an email to Undark. “Then the question becomes: if you’re making all of these other changes to the way you’re doing things, what is the value-add of the technology?”

But from the beginning, critics have questioned ShotSpotter’s actual impact on handgun violence, its accuracy, and the reliability of SoundThinking’s closely guarded, proprietary data. Now a growing number of cities — including Chicago, believed to be one of ShotSpotter’s largest markets — are having second thoughts or abandoning their commitment to the strategy.

A statement SoundThinking public relations manager Jerome Filip provided to Undark, which he asked be attributed to the company, described ShotSpotter as a “vital tool in modern policing” that’s designed to supplement the 911 reporting system. “In more than 80% of all shooting incidents, 911 calls do not come in, leaving victims without necessary aid from first responders. ShotSpotter picks up where 911 leaves off, enhancing police response to shooting incidents, aiding in evidence collection, and ultimately saving lives.”

Piza said he was surprised by some of the results. He assumed that there would be a higher clearance rate for shootings. “And we just didn’t find that.”

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Of course, police officers and medical personal should assess subjects subdued by a TASER for injuries. Existing medical or psychiatric conditions and the use of alcohol or drugs in the suspect may lead to behavior or reactions after the use of the TASER that need medical evaluation.

The current -- either direct, DC, or alternating, AC -- is the rate at which electrons going down a wire travel per second. Alternating current is what is typically used in wall sockets and it's more dangerous, according to the Journal of the American Medical Association, causing more extreme muscle contraction.

At that time, more than 90 cities had adopted the technology developed more than 25 years ago by a San Francisco Bay area firm called ShotSpotter. Today, more than 160 cities are using the ShotSpotter technology, according to its parent company, now called SoundThinking.

TASERS, also called "electrical control devices," have been used by law enforcement since the mid-1970s, with the intention to help subdue resistant suspects without physical contact or the use of firearms.

“Gun violence victimization did not reduce in either Kansas City or Chicago following the installation of ShotSpotter,” said Piza. “We also found that shootings were no more likely to be solved in either Kansas City or Chicago following the installation of ShotSpotter.”

One notable study of ShotSpotter’s effectiveness in Chicago was conducted by the MacArthur Justice Center at Northwestern Pritzker School of Law, and assessed ShotSpotter dispatches in the city between July 2019 and April 2021. Eighty-nine percent of the notifications did not lead police to evidence of any gun crime. And about 86 percent of notifications led to no criminal charges at all. There were more than 40,000 total unfounded ShotSpotter deployments during that period.

Serious injuries represent less than one percent of injuries from TASERs, as noted in a 2009 study published in the Annals of Emergency Medicine that looked at more than 1,200 uses of conducted electrical weapons by law enforcement officers against criminal suspects.

Clemmons, the University of Denver public policy professor, wrote that “despite its rigorous method, this study echoed the results of many previous studies of gunshot detection technology (GDT) — that it seems to have no effect on serious gun crime.”

In late May, the City Council voted to take control of the contracting process for the city’s ShotSpotter system from the mayor’s office, effectively keeping the technology in place until at least November, when the contract is set to expire. But the council also ordered the Chicago Police Department to collect more data on ShotSpotter’s effectiveness before the contract is renewed. “We haven’t seen gun violence go down as a result of this system,” Jessie Fuentes, an alderperson, said during the meeting, according to the Chicago Sun-Times. “We only get reports of the sound detected.”

The technology determines the location of the gunfire — usually within several feet — using readings from three or more sensors. Algorithms use the speed of sound to determine the difference in “arrival” times.

In 2017, when Chicago began expanding ShotSpotter into about half of the city’s neighborhoods, mostly in Black and Hispanic communities with higher rates of firearm violence, there were very few independent studies on gunshot detection technology in general and none on Chicago’s s system.

City officials in Durham voted in March to reject a three-year contract extension for ShotSpotter after an evaluation from the Wilson Center for Science and Justice at Duke University School of Law. The study raised questions about ShotSpotter’s accuracy and impact on crime, even as it found the technology more than doubled the number of gunfire notifications, reduced police response times by more than a minute, and resulted in increased arrests. The study, which was not peer reviewed, concluded that it was unable to determine if the technology had prevented or reduced crime.

On skin, the most common affects are superficial burns or small puncture wounds, caused by the metal probes that deliver the current not being immediately pulled off after a person has been tased. Scrapes are often seen across the skin surface because the person shocked by the TASER my convulse uncontrollably.

For example, a current applied to the arm will be reduced to .001 percent of the original signal by the time it reaches the heart. TASERs have a 2 milliamp current and it takes at least 1,000 milliamps -- 1 amp -- to injure muscles, nerves and the heart. Higher amps, starting at 10,000 milliamps or 10 amps, cause the heart to stop and produce severe burns, according to the U.S. Centers for Disease Control and Prevention.

Taser gun

A taser is a battery-powered, handheld device which delivers a short, low-energy electrical pulse. Two electrode wires are attached to the gun's electrical circuit. Pulling the trigger breaks open a compressed gas cartridge inside the gun and flings the electrodes into contact with a body and a charge flows into the muscles.

“The mayor ran on a platform and he believes that he is doing what he should,” Tom Chittum, SoundThinking’s senior vice president of forensic services, said in an interview with Undark. “But I think our view is removing ShotSpotter from Chicago would be a tragic mistake that would just result in more lost lives in a city that’s already suffered too much gun violence.”

For people without heart isssue, the electrical discharges of the TASER device are too short to affect the heart muscle or cause abnormal heart rhythms. Even for those with heart conditions, the proper use of the device does not appear to cause issues. One of the first study of TASERs on humans, published by the Academy of Emergency Medicine in 2006, looked at their effect on individuals with a known heart disease or diabetes. The study participants were shot in the back with a TASER and researchers measured blood markers of heart damage and did a test called an EKG, or electrocardiogram. They did not find any negative effects.

TASER self defense

Brandon Johnson, who was elected mayor of Chicago in 2023, vowed during his campaign to curb some mass surveillance tools such as speed cameras and gunshot detection technologies. Johnson has described the ShotSpotter system as expensive and ineffective.

However, TASER currents don’t reach the heart. Humans have protective mechanisms: The skin, which provides high resistance to electricity, and soft tissue, which surrounds muscles and organs like the heart, also reduce the current.

According to a 2024 analysis by an interdisciplinary research team, gunshot detection technology has had “no effect” on both fatal and non-fatal shootings in Chicago.

“Unsolved homicides and non-fatal shootings are exceptionally damaging to public safety and the community’s trust of police,” Ajenai Clemmons, a University of Denver public policy professor whose research focuses on police-community relations, wrote in an email to Undark. “If there are better strategies and tools for solving these cases, then money should be shifted there rather than to a technology that is expensive to install and maintain, whose benefits remain unclear, and whose effects would always need to be paired with changed officer behavior in order to work.”

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More than seven years ago, when the city of Chicago began its broad deployment of acoustic technology to identify and locate gunfire in high-crime neighborhoods, supporters promoted the system — which uses acoustic sensors, GPS software, and machine learning algorithms to alert the police in real-time — as an effective way to reduce handgun violence.

Researchers have reached similar conclusions in several other cities, including Kansas City, Missouri; Portland, Oregon; and Durham, North Carolina, where officials recently voted to end the city’s gunshot detection pilot project.

Since then, there has been a steady stream of research into the technology’s effectiveness. According to a 2024 analysis by an interdisciplinary research team at multiple institutions including Northeastern University and the University of Tampa, the system has had “no effect” on both fatal and non-fatal shootings.

TASERs cause muscle contractions, but do not appear to trigger the release of the muscle enzyme associated with muscle cell damage -- creatine kinase. If levels of that enzyme are high, it causes a condition called rhabdomyolysis, which can lead to kidney failure. Current research has shown that the muscle contractions induced by the TASER cause a small increase in CK, but do not appear to pose a direct risk for rhabdomylosis, according to a review of research by Forensic Science International.

“Without a positive impact on gun violence prevention, the next best benefit we could hope for would be improvements in clearance rates of violent gun crime cases,” wrote Clemmons, who was not involved in either study. “What we still need to know is whether the increased number of guns recovered by police translates into more cases solved and more shooters charged.”

Meanwhile, an audit conducted by the New York City Comptroller in June found that ShotSpotter “is overwhelmingly inaccurate and leads officers to spend hundreds of hours each month investigating nonexistent shots,” according to The New York Times.

The ShotSpotter system uses a battery of microphones and sensors installed high above street level to record, identify, and locate the source of potential gunshots. The sensors are usually on rooftops, the sides of buildings, or on top of streetlights or utility poles. They are trained to recognize the two distinctive audio signatures of gunfire. The first is the muzzle blast from the bullet exiting the chamber. The second audio signature is the distinctive waveform.