CEW Darts In The Eye: First Thorough Study Documents Risk

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In the first study of its kind, a research team has comprehensively documented the risk of barbed darts from conducted electrical weapons penetrating the eyes of suspects.

While certainly cringe-inducing, the risk, in fact, is small: only 1 in every 123,000 CEW discharges in the field results in eye injury, the study reports. But the problem is still considered “significant” because of the severe damage typically inflicted.

The majority of penetrating strikes result in the eyeball having to be surgically excised or remaining in place blinded. Indeed, probe impalement of an eye appears to be “the most common life-altering injury from electrical weapons,” the study’s lead author, Dr. Mark Kroll, told Force Science News.

Not included in the researchers’ statistical calculations are accidental eye injuries to officers and their family members that the team uncovered during their investigation.

Two officers, for example, unintentionally fired a probe into one of their own eyes during CEW training. Another, off duty, shot a dart into the eye of his teenage stepdaughter while showing her how to spark-test his CEW; he ended up charged with “knowing and reckless child abuse.” Another officer’s two-year-old girl suffered a permanently “shrunken, nonfunctioning eye” after a probe was discharged by siblings playing with the weapon.


When the team assembled by Kroll, an adjunct professor of biomedical engineering at the U. of Minnesota and the California Polytechnical Institute, began its work, only eight cases of penetrating eye injury from on-duty CEW discharges had been reported in medical literature.

After surveying some 500 master TASER instructors across the US and abroad and thoroughly canvassing open-source news media and legal databases, the researchers discovered 20 more, including cases from Australia, Canada, and Scotland. Thus, a documented total of “28 such injuries out of [an estimated] 3.44 million [CEW] field uses,” Kroll writes, “giving a demonstrated risk of approximately 1:123,000.”

Eighteen of the injuries resulted in total blindness in the affected eye, “primarily from globe rupture”; in 12 of those cases, the eye had to be removed. In addition to these 18, seven suspects were left with only partial vision. In just two cases could the researchers confirm that normal sight had been restored by surgical repair.


The injured parties mostly ranged in age from late teens to early 30s and often were mentally ill or suicidal, Kroll notes. Their eyes were not deliberately targeted by officers but unintentionally became points of impact because of unexpected or erratic movement, a miscalculation of probe spread, or fluke circumstances.

Examples from 20 cases described in the study:

  • A middle-aged male was stabbing himself in the neck with a box cutter when an officer sought to control him with a CEW discharge. The moving blade just happened to intersect the incoming probe and deflected it into the man’s eye, blinding him.
  • Another suspect ducked to tackle an officer just as the officer was deploying his CEW. When a probe hit the subject’s eye, he yanked it out and ran away. Arrested weeks later by the same officer, he reported “only mildly blurred vision in the injured eye.”
  • A severely intoxicated (0.31 BAC) domestic-violence suspect was struck in the eye by a probe intended for his center mass. He “denied the presence of the probe in his eye even after being informed” it was there. “Non-consented surgery” removed it.
  • A bar fighter was warned by a mounted officer of an imminent CEW discharge aimed at his lower shoulder blade. He turned and ducked, resulting in a probe ripping his right retina and leaving him partially blind.


A similar case of “sudden head-spinning movement” that caused a probe to strike an inmate in the eye during a jail-cell struggle ended up in a lawsuit cited in a legal section of the study added by Atty. Michael Brave. Here a federal appellate court concluded that “a police officer is not expected to always precisely hit his target when the target is moving,” Brave writes. (This 7th Circuit case is Forrest v. Prine, 620 F.3d 739 [2010].)

[Editor’s Note: Research by the Force Science Institute has established that a suspect can unexpectedly rotate his/her head in about 0.18 (18/100) of a second, with a fuller body rotation occurring in about one-third of a second. “This can easily create unpredictable strike points beyond an officer’s control,” says FSI’s executive director Dr. Bill Lewinski. For another real-world example of head-turning resulting in unintentional consequences, see Article #II below. Falling subjects can also pose a challenge as the result of having a head move from an erect position to suddenly moving through the plane of a projectile, such as a CEW dart, as discussed in an article on Force Science research titled, “Falling Subjects and the Use of Force,” published in the IACP’s The Police Chief magazine.]

A critical factor in eye-related litigation, the researchers point out, will be the intent of the officer involved. Any intentional CEW discharge into the head, face, or eyes should be avoided except in the most dire circumstances, they warn. “Significant legal justification” will be required.

In unintentional cases, “the officer’s objective in launching the projectile, the targeting point, and the totality of circumstances are important components in determining whether a projectile affecting the eye is legally justifiable,” the study states.

Nearly nine years ago, TASER International (now known as Axon), the major manufacturer of CEWs, lowered the preferred point of aim from the torso center to lower-center, in part to lessen the risk of probe placement into undesirable areas, including the head and face.
Even so, Axon warns: “Probes may deviate. CEWs are not precision-aimed weapons.”

The study, titled “Eye Injuries from Electrical Weapon Probes: Incidents, Prevalence, and Legal Implications,” appears in the Journal of Forensic and Legal Medicine. A free abstract and a link for purchasing the full report can be accessed by clicking here.

Dr. Kroll, a member of Axon’s scientific advisory board, can be reached at:mark@kroll.name.

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