New Study Of Unanswered Question: Do CEW Darts Cause Infections?

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More than 3.3 million darts from conducted energy weapons, including thousands that likely were contaminated with Staphlococcus aureus bacteria, have penetrated human skin. How many would you guess have caused infections?

The best guess would be “zero,” according to what is believed to be the first scholarly paper to review this issue.

The research group, headed by Dr. Mark Kroll, a biomedical engineer with the University of Minnesota and California Polytechnic University, reports its findings in the peer-reviewed Journal of Forensic Sciences.

Because of skin penetration by non-sterile CEW probes, “there has been concern raised about the risk of infection,” Kroll writes. Allegations of non-fatal infection have been made in at least two lawsuits.

But after a thorough review of CEW-related literature, including “a vast number of conference abstracts,” and a survey of individuals who experienced probe penetration, Kroll told Force Science News that those allegations are “poorly supported.”

In reality, he states, “The results of this paper suggest that probe infections have yet to occur and are extremely unlikely.”

(Kroll is a scientific advisor and board member of TASER International, the principal CEW manufacturer, and two other members of his team also have TASER connections. He has authored numerous reports of objective data related to CEW performance and outcomes.)


During the normal process of CEW manufacture, Kroll explains, the stainless steel dart portion “is grasped by an ungloved assembler for insertion into the cartridge,” thereby potentially adding human-borne “pathogens to the airborne pathogens that the probe is already exposed to.”

Other researchers have found that in the process some 5% of probes are contaminated with infectious Staphylococcus aureus bacteria, which can cause a multitude of diseases. This is not surprising, Kroll maintains, considering that some 80% of healthy people unwittingly are “persistent” or “intermittent” carriers of Staph germs.

In the field, Kroll calculates, an estimated 165,000 probes have penetrated human skin while laden with Staph bacteria.

“Inoculation by puncture with a bacteria-coated probe should be more likely to cause infection than a superficial scratch or a more open wound experienced in daily life,” Kroll notes. Yet his team’s investigation failed to establish any connection between CEW “landings” and infectious disease.


Through law enforcement agencies that “typically used a probe exposure as part of training,” the researchers surveyed the recipients of 238 probe punctures. The subjects were a mixture of races, and their probe penetrations had occurred from less than a month to more than a year before the survey.

The day after the exposure, “a slight majority of respondents noticed nothing at the landings, while about half noticed either redness or a burn mark.” Within a week, this “damage” for most had vanished. After a year, a few reported “a small scar” as evidence of penetration. Only one had sought medical aid, but none experienced any infection.

Kroll’s team also tracked down details of 11 dramatic published cases in which “significant probe penetrations into [especially] sensitive tissue” have been cited. These included probes that lodged in the brain, the eye, the chest (probe embedded so deep it had to be surgically removed), and the trachea. Again, “There were no case reports of infections”–a finding that is “indeed impressive,” Kroll writes.

Kroll believes that in “most, if not all” of the extreme cases, the subjects were given “prophylactic antibiotic treatment.” But the survey group received only “self-treatments,” which ranged from a mere “alcohol wipe” to “nothing.”


The researchers speculate on why probe penetration seems not to lead to infection.

  • The most important factor, Kroll suggests, is a sterilizing effect on the darts from the CEW’s electrical currents. “However, 10% of the time, only a single probe makes a connection and thus there is no current,” he says.
  • Bacteria colonies that are on the probe “spear” are “possibly very small and hence present a minimum challenge to the subject’s immune system.” Indeed, many superficial Staph infections “in otherwise healthy individuals will resolve without complication or need for medical attention.”
  • The “vast majority” of CEW penetrations do not enter bone or major blood vessels where the risk might be greater. “The most common bone penetration,” Kroll notes, “is that of the sternum,” and that occurs in fewer than 1% of probe contacts.

These speculations are “seeds for further research,” Kroll states.

Meanwhile, whatever the explanation, the lack of infections is “fortuitous,” he declares, because “there is no practical way to keep the probes sterile [during manufacture or use] with present technology.”

Click here for a free abstract of the paper, “Infection Risk from Conducted Electrical Weapon Probes: What Do We Know?” A link to the full article can be activated there for a fee.

Dr. Kroll can be reached at: mark@kroll.name

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