Mission Statement - De-Spinning the Pro-Taser Propaganda

Yeah right, 'Excited Delirium' my ass...


The primary purpose of this blog is to provide an outlet for my observations and analysis about tasers, taser "associated" deaths, and the behaviour exhibited by the management, employees and minions of Taser International. In general, everything is linked back to external sources, often via previous posts on the same topic, so that readers can fact-check to their heart's content. This blog was started in late-2007 when Canadians were enraged by the taser death of Robert Dziekanski and four others in a short three month period. The cocky attitude exhibited by the Taser International spokespuppet, and his preposterous proposal that Mr. Dziekanski coincidentally died of "excited delirium" at the time of his taser-death, led me to choose the blog name I did and provides my motivation. I have zero financial ties to this issue.

Thursday, January 3, 2008

Significant DC Component in Taser X26 Waveform...

Taser, in response to Ruggieri (Reference A below), have stated that the taser waveform is high frequency (50 or 100 kHz), and because of this factor (among other factors such as duty cycle) it provides a 100:1 safety advantage over the electrocution standards applicable to normal AC power-line frequencies as quoted by Ruggieri.

Reviewing the X26 waveform graph released by Taser (LG-STND-TECDBEC-001 Rev: C) makes it obvious that there is a significant Direct Current (DC, is zero Hz) component during the pulse (which would produce a significant 19 Hz component, and harmonics, on a longer time scale).

The graph below (graphically-edited for clarity) has been extrapolated to the right according to the textual description of the decay factor time constant to capture more of the obvious DC component (red) contained in the relatively long decay tail.

The amount of this DC component can be visually estimated by imagining the amount of negative offset (in the vertical current scale) that would be required to equalize the red and blue areas. It is obviously significant.

Many electrical engineers would probably describe this waveform as a DC pulse with a bit of 100kHz noise on the leading edge.

Taser X26 DC Component (click to enlarge)

[Copyright Note: Fair Use is claimed for a variety of reasons including but not limited to education, criticism, public safety, etc.]

The precise amount of the DC component can be calculated by performing a Fourier transform (or something similar) on the data extracted (manually, a big job) from the graph. The time scale becomes an issue and the expert making this calculation should be extremely careful to distinguish between averages and peaks, and the various time scales involved. For example, to include the spectrum component at 19 Hz (the pulse repetition frequency), it becomes necessary to run the analysis over much longer periods (probably five seconds).

Obviously, for legal purposes, the person making these calculation should have a name that starts with 'Professor'. I am not qualified to make any such statements except to note that, "Golly, there sure is a lot more red than blue, eh?" The experts can take it from there.

In conclusion, the taser X26 waveform (for example) appears to contain a significant DC component during the 19 Hz pulse. The waveform cannot be fairly described as simply 50 or 100 kHz.

Taser will probably find it difficult to walk away from some (or most?) of a '100:1' safety factor. I'm not sure, but I don't think I've seen anything that indicates that their claimed safety factor was even that high to begin with. If true, then there won't be much left after this.

Taser makes no mention of anything but 50 or 100 kHz. But it appears that they must have failed to properly analyze the waveform because it seems apparent that the waveform contains a significant percentage of much lower frequencies such as DC or 19 Hz. Has anyone ever seen a spectrum chart (frequency domain) of the X26 waveform?

This is the sort of information that a government regulator (hello?) might ask to see before approving (hello?) such a device for sale.

Holy sh_t. I think that I've found a smoking gun...

Reference A:


Analysis Claiming 'TASER™ Danger' Miscalculates Safety Threshold by Factor of 100

Report Applied Incorrect Standard to Evaluate TASER Output

SCOTTSDALE, Ariz. - TASER International, Inc. (Nasdaq: TASR), a market leader in advanced non-lethal devices, today responded to a report presented at the American Academy of Forensic Sciences conference in New Orleans wherein Mr. James Ruggieri presented an erroneous paper claiming that the electrical output of the TASER M26 is above the fibrillation threshold for 50% of the population.

"Mr. Ruggieri made a significant miscalculation, leading him to an insupportable conclusion," noted Max Nerheim, Vice President of Research and Development for TASER International, Inc. "Mr. Ruggieri's assertions are predicated on published safety guidelines in International Electrotechnical Commission (IEC) 479-1. Unfortunately, the standards published in IEC 479-1 are only applicable to low frequency, continuous duty cycle, AC electrical currents of less than 100 Hz, such as one would experience from an electrical wall outlet and not the output one would receive from a TASER device. Rather, the TASER M26 output is a pulsed, damped sine wave current with a frequency equivalent to 50,000 Hz. High frequency and pulsed outputs are covered under IEC 479-2, which indicates that the fibrillation threshold for currents similar to the TASER M26 are 100 times greater than the standard in IEC 479-1 errantly used by Mr. Ruggieri," continued Mr. Nerheim.

"In fact, there are three separate methodologies within IEC 479-2 which demonstrate the TASER M26 output to be significantly below the IEC fibrillation threshold. The appropriate standards under IEC 479-2 are consistent with data from both animal experiments and over 100,000 human volunteers, including myself and every other senior manager and engineer at TASER International, without a single incident of ventricular fibrillation. This is also backed by the over 66,000 actual field use applications by law enforcement. His misrepresentation was further evidenced by the remarks and questions raised by medical experts in attendance. It is disappointing that Mr. Ruggieri chose not to allow us to provide this technical feedback by reviewing his opinions before presenting them in a public forum."

"Furthermore, I was surprised that Mr. Ruggieri did not notice the error with his results as they are diametrically opposed to the dozens of independent studies of numerous government agencies that have concluded the TASER system, while not risk free, is generally safe. We invite interested readers to download a more in-depth analysis of this topic at http://www.taser.com/savinglives," concluded Mr. Nerheim.

PS: The 100,000 volunteers probably didn't have the taser shock applied to their chest with the barbs placed in the worst case positioning. This makes those 100,000 examples irrelevant to the discussion. If they're relying on barb positioning statistics for their actual field safety, then they should admit it. And stop claiming a higher level of inherent safety.

All 'in my opinion'.

No comments: