Some technical observations summarized

I've been following the taser issue since late-2007 when we had five taser-associated deaths in Canada in three months. Here are highlights of some technical observations I've made along the way.


The X26 taser actually emits about 150mA when measured using industry-standard RMS measurement techniques. This RMS value was mentioned on early revisions of the X26 taser specification sheet. But they subsequently and curiously expunged the RMS values from their specification sheets, and replaced it with the 2 mA "average" value. Obviously "2mA" sounds a lot safer than "150mA". But applying averages to complex electrical waveforms is widely considered to be misleading in the electrical engineering world.


Another detail that I found during my review of the technical information is that the X26 taser waveform, unlike the older M26 taser, contains a possibly-significant low frequency spectral component at the low frequency 19 Hz pulse repetition frequency. The low frequency spectral component is caused by unipolar (DC) pulse right after the arc phase. This spectral component is also 100% continuous duty cycle. It's new to the X26 taser introduced in 2003.

This finding is very intriguing because Taser International had previously claimed that the older (1999) M26 taser was safe "because" the output was high frequency and very low duty cycle. And then they walked away from these two "safety features" with the newer X26 introduced in 2003.

Coincidentally, 2003 is about the same time that the 'taser-associated' death issue started. Taser-associated deaths ramped up from well under one per month to about seven per month.


Dr. Mark Kroll, one of Taser's leading lights, wrote an article in IEEE Spectrum (Dec 07) where he submitted that the taser's very low duty cycle (he used the word 'chronaxie') was a key safety factor. He appears not to realize the implications of the X26 waveform. The duty cycle of the more-dangerous low frequency 19 Hz (and harmonics) spectral components are 100% continuous duty cycle for the entire 5+ second duration of each deployment cycle.


Also, I've received information that indicates that Kroll & Taser consider the shared anatomical features of all humans to be an additional safety factor. They appear not to realize that the safety standards are already designed around humans. They appear to be double-dipping.


Based on my review of the technical information, it sure seems that much of the real world safety factor is based on external factors (such as random dart placement). Perhaps this explains the strange observation about taser training sessions and demonstrations - they ALWAYS taser the trainees in the BACK, and they essentially NEVER taser them in the CHEST.

If they're so confident of the inherent safety of the taser, then they must have all the trainees henceforth turn around to be tasered directly in the chest. They can use clips instead of darts if they wish.


In my opinion, their claims of safety are, over time, obviously self-contradictory. It also really seems that they've made some strange design decisions that appear to reduce the real-world safety margins.


The studies they refer to typically only provide evidence that there is not a "high risk" of death. Well duh, we're talking about a low to moderate risk of death. So these studies are trumped by the real world results. Adjust for when X26 darts actually hit chest, and the risk numbers are many orders of magnitude higher than they claim.


And all this is related to just one aspect (electrical safety) of the larger taser issue that I've explored.