The stun gun shocks without killing--but how safe is it? Two experts take a look
IEEE Spectrum magazine - December 2007 [LINK]
By Mark W. Kroll [LINK][LINK], Patrick Tchou
[technical errors highlighted]
...about 1 percent of what's needed to cause the heart of the typical male to fibrillate. So the Taser's average current is far from the danger zone for healthy human hearts. ...a Taser's 100-us pulses are such a small fraction of the heart's chronaxie... ...you wind up with a pretty large margin of safety.
Compare and contrast the above wildly-inaccurate claims with what was released on May 1st, 2010:
Taser International admits that tasers can kill [LINK]
The basic technical mistakes are:
1) Assuming that "average" waveform currents are applicable when in fact the correct measurement would be 'effective'. Nobody knows exactly what the effective current is, but it seems likely to be in the range of about 30 to 50 mA considering the effects. The RMS current is about 150 mA, that's clearly not right either (a bit too high). But the "average" of about 2mA is also clearly not the correct measure (duh-obviously too low, considering the effects). See [LINK].See also [LINK].
2) Forgetting Fourier and failing to consider that the DC pulse after the arc phase is low frequency and thus those spectral components are continuous 100% duty cycle [LINK]. So the incorrectly-assumed chronaxie safety factor disappears for all low frequency spectral components. Even mentioning "chronaxie" without addressing the DC pulse is an obvious oversight. Again, nobody knows exactly what percentage of the current is low frequency and what percentage is high frequency. But this blogger was (as far as I know) the first to point out that the "experts" at Taser International appear to have slept through the Fourier class during EE 101.
These errors are really quite elementary.
And these errors perfectly explain the apparent discrepancy between what Kroll et al erroneously believed (that tasers were cardiac safe by a wide margin), and the cold hard fact that they aren't as safe as was claimed.
I don't mind dumb errors, but when combined with hubris...
*** An URGENT call to IEEE Spectrum ***
This above referenced article, especially the section written by Dr. Mark Kroll where he argued that tasers are essentially cardiac-safe, should be formally retracted, or somehow marked as "taser safety claims now known to be incorrect".
Taser International, in their latest training bulletin released 1 May 2010 [LINK], has abandoned their long-standing position that tasers are essentially inherently safe. They now formally acknowledge that tasers can significantly affect the heart if a dart happens to land too close. They also now acknowledge that tasers may cause acidosis. And they acknowledge that these are potentially lethal impacts.
The position taken by Kroll in this article was wrong at the time, and has now been contradicted by the position recently adopted by Taser International themselves. Again, see [LINK].
Because of the human-safety aspect to those false claims of taser safety, it is essential that this article be formally acknowledged as being wrong in those areas where Kroll argued (incorrectly) that tasers are essentially cardiac-safe.
This situation represents an important test for the editors and management of IEEE Spectrum to demonstrate the basic ethics that are such an important part of engineering where it intersects with human safety.
Safety claims now revealed to have been incorrect MUST be formally corrected.