
Introduction—We have previously published on the
ventricular fibrillation (VF) risk with TASER®
X26 conducted
electrical weapon (CEW). Our risk model accounted for realistic
body mass index distributions, modeled the effects of partial or
oblique dart penetration, and used epidemiological CEW
statistics. As new CEWs have become available to law
enforcement, their cardiac safety profile was not quantified.
Therefore, we applied our VF probability model to evaluate
their cardiac risk.
Methods and Results—An eXperimental Rotating-Field
(XRF) waveform CEW and the X2 CEW are new 2-shot
electrical weapon models designed to target a precise amount of
delivered charge per pulse, 64 µC and 62 µC, respectively. They
can deploy 1 or 2 probe pairs, delivered by 2 separate cartridges.
New Smart Probes (SP), which carry 11.5 mm long CEW darts,
can be used with XRF and X2 CEWs. Finite element modeling
(FEM) was used to approximate the current and charge densities
produced by XRF and X2 CEWs in tissues located in the vicinity
of darts, including accounting for the effects of fat, anisotropic
skeletal muscles, sternum, ribs, and lungs. Using our previous
cardiac risk probabilistic model, the new XRF and X2 CEWs
operated with 11.5 mm SPs, had an estimated overall theoretical
VF risk of less than 1 in 1 300 000 and 1 in 1 490 000 cases,
respectively. We also found that the XRF and X2 CEWs had
increased cardiac safety margins with respect to those previously
reported for the X26 CEWs when all three CEW models were
operated with 9 mm CEW darts. Lastly, the cardiac risk of these
new CEWs (< 0.76 ppm) was found to be much lower than
reported levels of CEW non-cardiac fatal injuries (e.g. falls and
burns, > 7.2 ppm).
Conclusions—While not risk-free, the new TASER XRF and
X2 CEWs offer increased cardiac safety margins and extremely
low cardiac risk profiles.
Keywords: Cardiac Risk, CEW, Fibrillation, Finite Element Model, TASER.
I. INTRODUCTION
Conducted electrical weapons (CEWs) are popular law
enforcement, military, and civilian force options. We have
previously published on the cardiac fibrillation risk with the
TASER®
X26 CEW [1]. Our risk model accounted for
realistic body mass index (BMI) distributions, used a new
model of effects of partial or oblique dart penetration and
factored in epidemiological CEW statistics [1]. Two new
next-generation Smart-Weapon CEWs, the eXperimental
D. Panescu is Chief Technical Officer, Vice President R&D at HeartBeam,
Inc. (e-mail: panescu_d@yahoo.com). Dr. Panescu is a paid consultant to
Axon Enterprise, Inc. (Axon), [formerly TASER International, Inc.
(TASER)].
M. W. Kroll is an Adjunct Professor of Biomedical Engineering at the
University of Minnesota, Minneapolis, MN (e-mail: mark@kroll.name). Dr.
Rotating-Field (XRF) waveform CEW, which is in
development, and the X2 CEW, already available, have been
studied. Both the XRF and X2 CEWs utilize charge metering
and pulse calibration to target a precise amount of delivered
charge per pulse, 64 µC and 62 µC, respectively [2, 3]. They
use electronic circuits to measure the charge delivered by the
previous pulse. The targeted charge delivery of the next pulse
is then controlled accordingly so that it is tightly adjusted
toward the specified charge value. Both CEWs use 2 cartridge
bays in order to provide for immediate back-up shots, if
determined necessary by the deploying officer.
The XRF CEW drives electrical stimuli along 4 field
vectors in a rotating sequence, as illustrated in Fig. 1. The dart
numbers correspond to the cartridge bay number. First pulse
of the sequence is delivered between darts 1+ and 1-. Second
pulse of the sequence goes from dart 1+ to dart 2-. Third pulse
is applied between darts 2+ and 2-. Fourth pulse crosses from
dart 2+ to dart 1-. Then the sequence repeats itself. There are
11 pulses per second (pps) delivered across each of the 4
vectors. Hence, under normal operation, each dart discharges
at a rate of 22 pps.
Figure 1. Rotating pulse-drive sequence for the XRF CEW (figure
shows an illustration of a CEW, not the actual XRF CEW).
The rotating pulse-drive sequence is designed to increase
XRF weapons efficacy. Even when XRF is deployed from a
Kroll is a consultant to Axon, and a member of the Axon Scientific and
Medical Advisory Board (SMAB) and Corporate Board.
M. A. Brave is Manager/Member of LAAW International, LLC, and is an
employee of Axon, Director of the Axon Science and Medical Research
Group, and legal advisor to the Axon SMAB and the Axon Training Advisory
Board (e-mail: brave@laaw.com).
All authors have served as expert witnesses for Axon or law enforcement.
New Conducted Electrical Weapons: Finite Element Modeling of Safety
Margins
Dorin Panescu, Ph.D., Fellow IEEE, Mark W. Kroll, Ph.D., Fellow IEEE,
and Michael A. Brave, M.S., J.D., Sr. Member IEEE
978-1-5090-2809-2/17/$31.00 ©2017 IEEE 2170
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
closer distance to a subject, the cross vectors #2 (darts 1+ to
2-) and #4 (darts 2+ to 1-) are likely to have a dart spread
greater than 30 cm, a distance which has been empirically
found to produce a more efficacious motor-nerve mediated
muscular effect [4].
Additionally, new Smart Probes (SP), with 11.5 mm CEW
darts, have been released for law enforcement use. The darts
of these Smart Probes have been newly designed and are 2.5
mm longer than the older 9 mm CEW darts, and 1.5 mm
shorter than the XP darts. The SPs are expected to be more
effective in penetrating through, and adhering to, subjects’
clothing.
In this study, we applied the previously published cardiac
safety probabilistic model to evaluate the ventricular
fibrillation (VF) risk of these two new next-generation SmartWeapon
CEWs, the XRF CEW and the X2 CEW when
operated with 11.5 mm Smart Probes.
II. METHODS
A. Summary of the CEW cardiac risk probabilistic model
Our VF risk probabilistic model was described in detail
previously [1]. In summary, computing CEW cardiac risk
involved the following steps:
1. Estimate applicable CEW thresholds for VF (VFT);
2. Use Finite Element Modeling (FEM) to estimate the maximal
distance from the tip of a CEW dart to the tissue region (MaxDTH)
still exposed to the VFT charge levels. The analyses included
realistic tissue types around the dart (e.g. fat, sternum, ribs,
intercostal muscle and lungs) and their electrical material
properties, including the anisotropy of the skeletal muscle;
3. Estimate the skin-to-heart distance (STH) required for VF
induction;
4. Estimate the effects of oblique skin penetration angles of CEW
darts on STH;
5. Based on published BMI distributions, compute the probability of
a subject having a STH in the range required for VF induction;
6. Based on epidemiological data, compute the probability of a
subject being hit by CEW darts in the chest region having narrow
STH;
7. Compute overall CEW cardiac risk; and
8. Correlate with existing epidemiological statics for consistency.
B. XRF and X2 CEWs output parameters and VFTs
Figures 2 and 3 show the output current and voltage
waveforms of the XRF and the X2 CEWs. Table I summarizes
XRF and X2 CEWs electrical output parameters relevant to
cardiac risk analyses. Formulas (1) and (2) apply the VFinduction
strength-duration theory to compute the thresholds
for direct VF induction by XRF and X2 CEWs. We have
previously explained these formulas in detail [1]. They were
based on extensively published data [5 – 10].
The current density VFTs were:
XRF_VFTJ = 7 mA/cm2
*(1+1.2 ms/0.05 ms) = 175 mA/cm2
(1a)
X2_VFTJ = 7 mA/cm2
*(1+1.2 ms/0.066 ms) = 134 mA/cm2
(1b)
TABLE I. Relevant output parameters of TASER XRF and X2 CEWs.
Figure 2. TASER XRF and X2 CEW current waveforms.
Figure 3. TASER XRF and X2 CEW voltage waveforms.
Correspondingly, the charge density threshold for VF
induction were computed as:
XRF_VFTQ = 7 mA/cm2
* 0.05 ms * (1+1.2 ms/0.05 ms) = 8.75 C/cm2
(2a)
X2_VFTQ = 7 mA/cm2
* 0.066 ms * (1+1.2 ms/0.066 ms) = 8.86 C/cm2
(2a)
Sugimoto et al. suggested that VFTs drop with an
increasing number of captured premature ventricular
responses [11 – 13]. With 4 captured premature ventricular
responses, the VFT may drop to about 3 times the cardiac cell
excitation threshold. We used the term premature ventricular
response VFT (pvrVFT) to separate this reduced threshold
from the VFT discussed above. Using the above rheobase and
chronaxie, we computed pvrVFTJ and pvrVFTQ:
XRF_pvrVFTJ = 3*1.48 mA/cm2
*(1+1.2 ms/0.05 ms)
Parameter XRF X2
Open-circuit peak voltage [kV] 50 52
Average Pulse Voltage [V] 770 560
Peak Main Phase voltage in typical load [kV] 1.7 1.2
Peak Main Phase current in typical load [A] 2.8 2
Energy delivered in typical load [J/pulse] 0.098 0.069
Power into 600 ohm load [W] 2.15 1.3
Net charge in the main phase [µC] 64 62
Impulse duration [µs] 50 66
Pulse rate [pulse/s] 22 19
2171
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
= 111 mA/cm2
(3a)
X2_pvrVFTJ = 3*1.48 mA/cm2
*(1+1.2 ms/0.066 ms)
= 85 mA/cm2
(3b)
XRF_pvrVFTQ = 3*1.48 mA/cm2
* 0.05 ms * (1+1.2 ms/0.05 ms)
= 5.55 C/cm2
(4a)
X2_pvrVFTQ = 3*1.48 mA/cm2
* 0.066 ms * (1+1.2 ms/0.066 ms)
= 5.62 C/cm2
(4b)
C. Finite Element Models for MaxDTH computations
We used 3-D FEM to understand the current density
distributions generated by CEW electrodes [14]. Thoracic
tissue distributions were for a thin body (Figs. 6 and 8):
• Tissue regions (dimensions reflect region thickness):
• Skin: 2 mm thick
• Fat: 6 mm thick
• Pectoral Muscle: 7 mm thick
• Sternum/Rib/Intercostal muscle: 11 mm thick
• Lung and connective tissue: 8 mm thick
• Cardiac tissue: 11 mm thick
• Model was 24 cm long, 20 cm wide and 4.5 cm thick
• Voltage boundary conditions: 1700 V (XRF) and 1200 V (X2)
• Model computed steady-state solution
• CEW dart electrodes – 9 or 11 mm long, 1 mm diameter,
embedded in tissue up to full length, 15 cm apart.
• Elements: 36480 hexahedral elements, spatial resolution 0.17 –
2.75 mm.
The distribution of tissues and their dimensions were based
on data from anatomic atlases and visible human databases
[15 – 17].
Table II shows the FE region resistivities, which were
based on previous published reports [18 – 21].
TABLE II. FEM material properties.
Region Resistivity [Ωcm]
Skin 5000
Fat 2500
Pectoral muscle x = 1000; y=z=200
Bone (sternum, rib) 1 000 000
Intercostal muscle x = 1000; y=z=200
Lung 1500
Connective tissue 500
Cardiac tissue 333
Electrode 0.001
MaxDTH was defined as the distance from the dart tip to
the farthest element that had a current density greater than
VFTJ and was mapped around the CEW dart tip.
Alternatively, MaxDTH was also computed and discussed
based on charge density distribution and thresholds, VFTQ.
The model was also used to analyze the current attenuation
effects of fat, anisotropic skeletal muscle, sternum and rib
layers had on MaxDTH. To account for the worst-case
scenario, we chose the XRF and X2 peak main-phase
voltages, 1700 V and 1200 V, respectively, as boundary
conditions, rather than the pulse-averaged voltages.
D. STH vs. BMI distributions
The distance between the skin surface and the
corresponding closest point on the heart, abbreviated
MinSTH, depends on the subject’s BMI. This dependency
was studied in detail by the Wisconsin and Cleveland groups
[22, 23]. Figure 4a shows the distribution MinSTH vs. BMI
measured using echocardiographic imaging by the Wisconsin
group in 55 male subjects [22]. Figure 4b shows the MinSTH
vs. BMI relationship, as measured using computer
tomography (CT) by the Cleveland group in 37 males [23].
Figure 4a. Wisconsin group MinSTH vs. BMI and ARD subject BMI
range [22].
Figure 4b. Cleveland group MinSTH vs. BMI and ARD subject BMI
range [23].
Males are by far the best represented gender during
encounters with law enforcement that result in deployment of
CEWs [24]. Both Figs. 4a and 4b mark the BMI range of 27
– 32 kg/m2
, corresponding to law enforcement temporal
arrest-related death (ARD) subjects [24].
E. CEW chest shot distributions from epidemiological data
We used the previously published epidemiological data to
compute the probability of CEW darts hitting the anterior
chest (Pchest) and then the conditional probability to land at
anterior chest locations where the heart is closest to the chest
surface (PZone_MinSTH) [1]. Figure 5 illustrates the anterior chest
area that was of interest for hit probability purposes. As in the
past, we reviewed epidemiological studies in order to collect
the relevant data [25 – 27]. We have also reviewed 24 cases
in which CEW darts were deployed to the anterior chest. In
all cases, the medical examiner reports or autopsy data were
used to document the actual location of the CEW darts and
the amount and angle of their penetration through the skin or
chest wall.
2172
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
Figure 5. CEW chest shot probabilities estimates took into account the
approximate location of the heart in a subject’s chest [26].
F. Cardiac risk computation
The same cardiac risk computation was employed, as
previously published [1]:
VFrisk = Pchest*PZone_MinSTH*PMaxDTHvsBMI*Pdart_penetrate (5)
where:
- VFrisk is the overall probability of VF induction with the
XRF or X2 CEWs;
- Pchest is the probability of hitting the anterior chest with CEW
darts, as per cited epidemiological studies;
- PZone_MinSTH is the conditional probability of hitting the area
of minimum STH, assuming the CEW dart landed on the
anterior chest;
- PMaxDTHvsBMI is the probability of a subject having a STH
shorter than the length of the CEW dart plus MaxDTH. This
probability was computed based on the MinSTH vs. BMI
distributions discussed in Figs. 4a and 4b; and
- Pdart_penetrate is the correction applied given that in the vast
majority of cases CEW darts do not penetrate the skin in
purely perpendicular mode and do not embed along their
full length, even when hitting the MinSTH zone.
III. RESULTS
A. MaxDTH to prevent VF induction
To evaluate the worst-case scenario VF risk, accounting
for the Sugimoto effect, the FEM was used to analyze at what
distance from the tip of CEW dart to the location where the
current density dropped below pvrVFTJ. Assuming a CEW
dart fully embedded into tissue, MaxDTH was 2.6 mm for the
XRF and 2.5 mm for X2, respectively. Figures 6(a) and 6(b)
illustrate the current density distribution around the tip of a
CEW dart. Thus, under worst-case circumstances, for a 9 mm
CEW dart, the STH would have to be at most 9 mm + 2.6 mm
= 11.6 mm for the XRF and at most 9 mm + 2.5 mm = 11.5
mm for the X2. For greater STH, the residual CEW currents
could not exceed pvrVF thresholds and VF could not be
induced, including when considering the effects of premature
ventricular responses. Figures 4a and 4b show STH
distributions with respect to the 11.6 mm line. Note that none
of the 92 patients had MinSTH less than 11.6 mm.
Figure 6(a). XRF CEW current density around a CEW dart fully embedded
in tissue. Red zone area where current densities were > pvrVFTJ.
Figure 6(b). X2 CEW current density around a CEW dart fully embedded in
tissue. Red zone area where current densities were > pvrVFTJ.
As such, when operated with 9 mm darts, both the XRF
and the X2 CEWs were not expected to be capable of inducing
VF in any of these patients. With Smart Probes, the minimal
STH would have to be at most 11.5 mm + 2.6 mm = 14.1 mm
for the XRF CEW and at most 11.5 mm + 2.5 mm = 14.0 mm
for the X2 CEW. For greater STH, the residual CEW currents
would not exceed pvrVF thresholds. Hence, VF could not be
induced, including when considering the effects of premature
ventricular responses. Figures 4a and 4b also show STH
distributions with respect to the 14.1 mm line. Note that only
one of the 92 patients had a MinSTH of 12.7 mm, which was
less than 14.1 mm. As such, when operated with 11.5 mm SPs,
assuming full and perfect perpendicular penetration through
the skin, directly anterior to the heart, with no intervening
clothing, the XRF or the X2 CEWs would have been
hypothetically expected to be capable of inducing VF in only
one of these 92 patients.
B. STH vs. BMI distributions
Based on data presented in Figs. 4a and 4b, we computed
PMaxDTHvsBMI. As defined above, this is the probability of a
subject having a minimal STH shorter than 11.6 mm, for
standard 9 mm darts, or shorter than 14.1 mm (XRF CEW) or
14.0 mm (X2 CEW), when 11.5 mm SPs were used. As seen
in Figs. 4a and 4b, out of 92 volunteers, none had MinSTH 
11.6 mm and only one experienced a MinSTH < 14.1 mm, or
12.7 mm to be precise. Hence, PMaxDTHvsBMI_9mm = 0/92 = 0%
and PMaxDTHvsBMI_11.5mm = 1/92 = 1.1%. The difference between
12.7 mm and 14.1 mm, or 1.4 mm, lies well within the imaging
2173
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
instrumentation tolerance. Thus, it may very well be that none
of the 92 volunteers exhibited a MinSTH effectively shorter
than STH required to induce VF or pvrVF. Also, no volunteers
with BMIs between 27 – 32 kg/m2
, such as those reported for
ARD subjects, had STHs less than 14.1 mm. Hence,
PMaxDTHvsBMI for practical, real field-use situations is much
lower than 1/92.
C. Effects of partial or oblique-angle CEW dart penetration
In the vast majority of cases, CEW darts do not penetrate
the skin in purely perpendicular mode, or do not embed along
their full length. We deployed CEWs in gel phantoms
simulating the human chest. Due to inertial effects, the darts
penetrated only 6 mm, on average, much shorter than
MinSTH distances observed in the cardiac imaging study.
Therefore, it made sense to provide an estimate for a
correction factor, Pdart_penetrate, which adjusted the overall
cardiac risk for incomplete or oblique CEW dart penetrations.
Figure 7 illustrates the trigonometry problem solved in
order to correct for the CEW dart penetration angle, , and for
its partial penetration factor, k.
Figure 7. Diagram shows CEW dart entering the skin towards heart at an
angle  and penetrating over a partial length, k*Lengthdart.
The geometric condition that must be met to induce VF
equated to:
k*Lengthdart*cos() +MaxDTHMinSTH (6)
where and 0 < k  1.
In other words, the sum of a partially penetrated CEW dart
length projection onto the vertical axis plus the maximal
distance from dart tip to the farthest VFTJ or pvrVFTJ contour
(i.e. MaxDTH) must exceed MinSTH. For Lengthdart = 9 mm,
there are no physical solutions to Eq. (6). Hence, as discussed
before, under such circumstance the XRF and X2 CEWs
would not be expected to induce VF in subjects according to
the STH distribution revealed by the cardiac imaging study
results discussed in section II.D. For Lengthdart = 11.5 mm 
cannot exceed 27° for XRF CEW and 26° for X2 CEW (i.e.
solution of (6) for k = 1). Forcing  = 0° provides the
respective range for k. Hence, 10.1/11.5 < k  1 for XRF CEW
and 10.2/11.5 < k  1 for X2 CEW. Where 12.7 mm – 2.6 mm
(2.5 mm) = 10.1 mm (10.2 mm). Thus, the  and k ranges
favorable to induction of pvrVF are:
° and 10.1/11.5 < k  1 for XRF&11.5 mm SP
° and 10.2/11.5 < k  1 for X2&11.5 mm SP
Outside these ranges, CEW darts are unlikely to present an
effective penetration depth which were sufficiently close to
the heart surface to induce VF. Solving for the probability that
 and k fall within their respective range yields Pdart_penetrate_XRF
= 1.7% and Pdart_penetrate_X2 = 1.5%. As a note, we have not
considered the reduction in penetration caused by subject’s
clothing. The subject’s clothing may reduce, on average, the
dart penetration depth by an additional minimum 1 – 2 mm.
Even assuming just 1 mm penetration depth reduction due to
clothing, there would be no physical solutions to Eq. (6) for
either the XRF or X2 CEWs. Consequently, the correction
factor Pdart_penetrate should be seen as a very conservative
estimate.
D. Chest shot distributions from epidemiological data
Epidemiological studies provided data about the frequency
of anterior chest hits during field uses of CEWs [25 – 27]. Out
of 1201 consecutive TASER X26 CEW deployment cases, 178
cases involved dart locations on the anterior chest area shown
in Fig. 5 [26]. None of these cases experienced documented
VF events, or any other cardiac rhythm disturbance [26].
These deployments were prior to the manufacturer lowering
the frontal preferred point of aim from center mass to lower
center mass in September 2009. Thus, there is reason to
assume that the above number for anterior chest shots would
be smaller for XRF or X2 CEWs. Also, since the XRF and X2
probe deploying mechanism, distance and velocity are
equivalent to those for the X26 CEW, we determined that our
previous Pchest estimate of less than 14.8% can be used for this
updated model. We have also reviewed 24 cases in which
CEW darts contacted the anterior chest, in the approximate
region circled in Fig. 5. In all cases, the respective medical
examiner reports or autopsy data were used to document the
actual location of CEW darts and the amount and angle of their
penetration through the skin or chest wall. Out of 24 cases, 18
had their respective darts fall within the anterior chest area
from Fig. 5. Out of these 2*18 = 36 dart locations, only one
came close to the left chest region where the MinSTH distance
could have been met. None of these cases had documented VF
induction caused by CEW use. Thus, we estimated PZone_MinSTH
to be less than 1/36, or 2.7%.
E. Overall cardiac risk with XRF and X2 CEWs
According to Eq. (5), if the XRF and X2 CEWs were used
with 9 mm CEW darts, the theoretical overall cardiac risk
would be extremely low because MinSTH distance conditions
for VF induction (i.e. MinSTH = 12.7 mm – per Fig. 4) would
not be met. With the XRF and X2 CEWs utilizing 11.5 mm
SPs, the theoretical cardiac risk computed as (ppm stands for
parts-per-million):
VFrisk_XRF_11.5mm = 178/1201*1/36*1/92*0.017
= 0.00000076 = 0.76 ppm
VFrisk_X2_11.5mm = 178/1201*1/36*1/92*0.015
= 0.00000067 = 0.67 ppm
equivalent to approximately 1 in over 1 300 000 cases for
2174
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
XRF CEW and 1 in over 1490000 for X2 CEW.
IV. DISCUSSION
We have previously employed this cardiac risk
probabilistic model to estimate the theoretical probability of
VF induction with TASER X26 CEWs with 9 mm darts [1].
With the X26 CEW, we determined that theoretical VF risk to
be less than approximately 1 in 2800000 cases. Due primarily
to pulse-metered and calibrated charge, the XRF and X2
CEWs deliver less charge than the X26 CEW with skin
embedded darts. Also, the respective pulse durations are
shorter. Hence, it was expected to find that the comparable
cardiac risk was lower with these new charge-metered smart
weapons. Indeed, with 9 mm darts, our model computed a
cardiac risk of 0 for the XRF and X2 CEWs vs. 1 in 2800000
cases for the X26 CEW. This result can be explained by noting
that the MaxDTH decreased from 4.3 mm for the X26 CEW
to 2.6 mm and 2.5 mm for the XRF and X2 CEWs,
respectively. These MaxDTH distances accounted for the VFT
reduction caused by multiple premature ventricular responses,
according to the Sugimoto effect [11 – 13]. As a consequence,
if the XRF or X2 CEWs were operated with 9 mm CEW
probes, the resulting electrical fields would not be expected to
reach deep enough to trigger fatal cardiac rhythms, except,
perhaps, in the thinnest subjects having extremely short STHs,
far outside ranges documented by cardiac imaging [22 – 24].
If operated with the new, 11.5 mm smart CEW probes, the
estimated theoretical VF risk for the XRF and X2 CEWs was
1 in more than 1.3 million cases, or less than 0.76 ppm. This
remains a very low level of cardiac risk. Between 2011 and
2016, there were approximately 180000 X2 CEWs sold in the
United States [3]. At the time of this article, the XRF CEW has
not yet been released to markets. Previous statistics gathered
from the field use of TASER CEWs show an average of 0.55
field uses/year/sold CEW [27]. Hence, we estimated that, todate,
there have been approximately 235 000 field uses of
Smart–Weapon CEWs. None of these have been confirmed to
result in inducing cardiac arrest. While, at this time, the field
use numbers are too low to support statistically significant
conclusions, the trend is supportive and consistent with the VF
risk estimated by our model.
Given that the XRF and X2 CEWs target a more precise
control of the delivered pulse charge, it is important to discuss
the implications of using charge density thresholds, VFTQ, in
estimating the cardiac risk. Figures 8(a) and 8(b) show the
charge density profiles corresponding to XRF and X2
pvrVFTQ, respectively. The pvrVFTQ thresholds are given in
Eqs. 4(a) and 4(b), respectively. The corresponding MaxDTH
distances, 1.75 mm (XRF CEW) and 1.67 mm (X2 CEW), are
on the border of falling short of providing physical solutions
for Eq. 6, including considering a dart length of 11.5 mm, such
as for the new Smart CEW Probes. Under worst case scenario,
assuming the entire 11.5 mm dart length has penetrated into
tissue, Eq. 5 yields a charge-density-based VF risk of < 0.2
ppm. Therefore, the risk estimates provided in section III.E
should be considered as highly conservative. Likely, real
cardiac risks with XRF and X2 CEWs are likely significantly
lower than the estimated < 0.76 ppm, perhaps even lower than
0.2 ppm.
Figure 8(a). XRF CEW charge density around a CEW dart fully
embedded in tissue. Red zone area where charge densities were > pvrVFTQ.
Figure 8(b). X2 CEW charge density around a CEW dart fully
embedded in tissue. Red zone area where charge densities were > pvrVFTQ.
Non-cardiac CEW risk levels, such as injuries or death
resulting from subjects’ often uncontrolled fall during
exposure to CEWs or such as fatalities caused by CEW
igniting gasoline fumes, are much higher than the theoretical
VF risks estimated above. Kroll et al. searched for ARD cases
with TASER CEW usage where fall-induced injuries might
have contributed to the death [28]. Their inclusion criteria
were:
1. Arrest-related or in-custody incident;
2. Death occurred;
3. CEW was used in the incident;
4. Decedent fell during the incident;
5. Traumatic brain injury contributed to or caused the death.
The inclusion criteria were met in 24 cases. Of those, 5 were
classified as “intentional” jumps (suicide or escapes) and
another 3 cases were excluded because of missing contributing
traumatic brain injury. In total, 16 cases with fatal brain
injuries were found to be caused by falls resulting from use of
CEWs. Compared to over 3 million cases of CEW field use,
the resulting fatal fall risk was estimated at 5.3 ± 2.6 ppm [28].
There have been 6 fatal cases caused by CEWs igniting
gasoline fumes or propane [29]. Over the estimated 3 million
cases of CEW field use, the resulting fatal burn risk was
estimated at 1.9 ppm [29, 30].
2175
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.
By comparison, our present study estimated the theoretical
conservative VF risk with XRF or X2 CEW to be less than
0.76 ppm (III.E). This is significantly lower than either the
fatal fall (5.3 ppm) or fatal burn (1.9 ppm) risks, or much lower
than the combined 7.2 ppm non-cardiac mortality risk.
Comparison with other epidemiological and risk assessment
studies have been provided in our previous [1, 29]. They are
applicable to and consistent with results of this current study.
V. CONCLUSIONS
To-date, there has been no undisputed medical evidence
linking causation of VF to use of CEWs. In general, CEWs
should not be considered risk-free force options. The new
XRF and X2 CEWs have extremely low cardiac risk profiles
and exhibit increased cardiac safety margins over the
previously analyzed X26 CEW model. Their estimated
theoretical conservative risk of VF induction, even when
considering effects of premature ventricular responses, is
likely to be significantly less than 1 in more than 1.3 million
cases, much lower than non-cardiac risk levels associated
with use of CEWs.
REFERENCES
[1] D. Panescu, M. Kroll and M. Brave, “Cardiac Fibrillation Risks with
TASER Conducted Electrical Weapons,” Conf Proc IEEE Eng Med
Biol Soc, vol. 2015, pp. 323-329, 2015.
[2] M. H. Nerheim, Systems and methods for an electronic control device
with date and time recording, US Patent 7,570,476, August 4, 2009.
[3] TASER International: Smart Weapons Technology. Available at
https://www.taser.com/products/smart-weapons.
[4] J. Ho, D. Dawes, J. Miner, S. Kunz, R. Nelson and J. Sweeney.
“Conducted electrical weapon incapacitation during a goal-directed task
as a function of probe spread,” Forensic Sci Med Pathol, vol. 8(4), pp.
358-366, 2012.
[5] H. Sun. Models of ventricular fibrillation probability and neuromuscular
stimulation after Taser® use in humans. PhD thesis: University of
Wisconsin, 2007. Available online: http://ecow.engr.wisc.edu/cgi-
bin/get/ece/762/webster/
[6] H. Sun, J. Y. Wu, R. Abdallah and J. G. Webster, “Electromuscular
incapacitating device safety,” Proc IFMBE, 3rd
EMBE Conference,
Prague, vol. 11(1), 2005.
[7] L.A. Geddes and L. E. Baker. Principles of Applied Biomedical
Instrumentation, 3rd Ed. New York: John Wiley & Sons, 1989.
[8] J. A. Pearce, J. D. Bourland, W. Neilsen, L. A. Geddes and M. Voelz,
“Myocardial stimulation with ultra-short duration current pulses,”
PACE, vol. 5(1), pp. 52-8, 1982.
[9] R. H. Zoll, P. M. Zoll and A. H. Belgard, “Noninvasive cardiac
stimulation,” In G. A. Feruglio, Ed: Cardiac pacing: electrophysiology
and pacemaker technology, pp 593-596, Padua: Piccin Medical Books,
1983.
[10] W. D. Voorhees, K. S. Foster, L. A. Geddes and C. F. Babbs, “Safety
Factor for Precordial Pacing: Minimum Current Thresholds for Pacing
and for Ventricular Fibrillation by Vulnerable-Period Stimulation,
PACE, vol. 7, pp. 356–360, 1984.
[11] Sugimoto, Schaal, and Wallace, "Factors determining vulnerability to
ventricular fibrillation induced by 60-cps alternating current," Circ Res,
vol. 21, pp. 601-608, 1967.
[12] International Electrotechnical Commission, Effects of current on human
beings and livestock: Part 1 – General aspects, IEC 60479-1, 2005,
Geneva: IEC.
[13] International Electrotechnical Commission, Effects of current on human
beings and livestock: Part 2 – Special aspects, IEC 60479-2, 2007,
Geneva: IEC.
[14] Structural Research & Analysis Corporation (SRAC), division of
SolidWorks Corporation, COSMOS/M:
http://www.cosmosm.com/pages/products/cosmosm.html
[15] J. P. Delille, A. Hernigou, V. Sene, G. Chatellier, J. C. Boudeville, P.
Challande and M. C. Plainfosse, “Maximal thickness of the normal
human pericardium assessed by electron-beam computed tomography,”
Eur Radiol, vol. 9(6), pp. 1183-9, 1999.
[16] R. S. Gautam, G. V. Shah, G. V., H. R. Jadav and B. J. Gohil, “The
Human Sternum – as An Index of Age & Sex,” J Anat Soc India, vol.
52(1), pp. 20-23, 2003.
[17] Lumen Cross-Sectional Tutorial by John McNulty:
http://www.meddean.luc.edu/lumen/MedEd/grossanatomy/x_sec/main
x_sec.htm
[18] D. Panescu, M.W. Kroll, C. Iverson, M. Brave, “Electrical Shielding
Effects of the Sternum,” Conf Proc IEEE Eng Med Biol Soc, vol. 2014,
pp. 4464-70, 2014
[19] D. Panescu, J. G. Webster and R. A. Stratbucker, “A nonlinear finite
element model of the electrode-electrolyte-skin system,” IEEE Trans
Biomed Eng, vol. 41(7), pp. 681–687, 1994.
[20] D. Panescu, J. G. Webster, W. J. Tompkins and R. A. Stratbucker,
“Optimization of cardiac defibrillation by three-dimensional finite
element modeling of the human thorax,” IEEE Trans Biomed Eng, vol.
42(2), pp. 185–192, 1995.
[21] S. Singh and S.Saha, “Electrical properties of bone. A review,” Clin
Orthop Relat Res, vol. 186, pp. 249-71, 1984.
[22] J-Y Wu, H, Sun, A, O’Rourke, S. Huebner, P. S. Rahko, J. A. Will and
J. G. Webster, “TASER dart-to-heart distance that causes ventricular
fibrillation in pigs,” IEEE Trans Biomed Eng, vol. 54, pp. 503-508,
2007.
[23] G. G. Bashian; G. A. Wagner; D. W. Wallick and P. J. Tchou,
“Relationship of Body Mass Index (BMI) to Minimum Distance from
Skin Surface to Myocardium: Implications for Neuromuscular
Incapacitating Devices (NMID)”, Circulation, vol. 116:II, pp. 947,
2007.
[24] S. J. Stratton, C. Rogers, K. Brickett and G. Gruzinski, “Factors
associated with sudden death of individuals requiring restraint from
excited delirium,” Am J Emerg Med, vol. 19, pp. 187-191, 2001.
[25] M. White, J. Ready, C. Riggs, D. M. Dawes, A. Hinz and J. D. Ho, “An
Incident-Level Profile of TASER Device Deployments in ArrestRelated
Deaths,” Police Quarterly, vol. 16, no. 1, pp. 85-112, 2013
[26] W. P. Bozeman, E. Teacher and J. E. Winslow, “Transcardiac conducted
electrical weapon (TASER) probe deployments: incidence and
outcomes,” J Emerg Med, vol. 43(6), pp. 970-975, 2012.
[27] J. E. Brewer, M. W. Kroll, “Field Statistics Overview,” in TASER
Conducted Electrical Weapons: Physiology, Pathology, and Law, M.W.
Kroll, J.D. Ho Eds., Springer, 2009.
[28] M. W. Kroll, J. Adamec, C. V. Wetli and H. E. Williams, “Fatal
traumatic brain injury with electrical weapon falls,” Journal of Forensic
and Legal Medicine, vol. 43, pp. 12-19, 2016.
[29] M. A. Brave, M. W. Kroll, S. Karch, C. Wetli, M. Graham, S. Kunz,
D. Panescu, “Medical Examiner Collection of Comprehensive,
Objective Medical Evidence for Conducted Electrical Weapons and
Their Temporal Relationship to Sudden Arrest,” World Academy of
Science, Engineering and Technology, International Science Index, Law
and Political Sciences, vol. 3(1), p. 527, 2017.
[30] C. Clarke and S. Andrews, “The ignitability of petrol vapours and
potential for vapour phase explosion by use of TASER® law
enforcement electronic control device,” Science & Justice, vol. 54, pp.
412-420, 2014.
2176
Authorized licensed use limited to: Charles University. Downloaded on October 10,2025 at 23:49:05 UTC from IEEE Xplore. Restrictions apply.