Tuesday, May 03, 2005

Criminals and GPS

It appears that in June the Corrections Department are going to trial monitoring offenders by satellite, amongst other techniques under investigation.

Most of the techniques I've read about recently make sense - such as anklets that transmit continuous radio signals to installed monitoring units, and voice-verification. You can read a little more on this page at the Corrections website.

Voice verification could be fooled with recorded messages if it isn't combined with some technique - such as RF monitoring to ensure the anklet is also in range, or a random phrase is asked for voice-verification each time. It appears that they are looking at the Israeli company PerSay providing the technology called FreeSpeech. Perhaps we may see this technology used for phone-banking and interaction with government agencies in the not too distant future?

Anyway, back to the GPS solution. It sounds as though the GPS units are designed to received the same RF signal that is transmitted by the RF bracelet - meaning the the GPS unit would activate an alarm if it is separated from the anklet, such as the offender removing it.

GPS signals however have limitations. They cannot be received in buildings, under tree canopies, and often fail in urban canyons such as central Auckland or Wellington. And you won't get a good clear GPS signal unless you mount the GPS receiver on the offenders head, otherwise their body will block some of the signals and the unit may not be able to triangulate its location. That includes when they are in vehicles too. Opps.

The upshot of this is that GPS tracking has only limited benefits for tracking offenders given the wide variety of ways signal can be lost - unintentionally or on purpose (try wrapping some tinfoil over the unit).

Which brings me to my point. If we can't trust people to wander around in the community without tracking devices, they shouldn't be in community fullstop. Otherwise, they'll just end up losing them.

I believe its just a cost-cutting measure to move criminals out into society, just like they have moved other 'institutional clients' into the community. I can't want to say I-told-you-so when the first offenders go missing with GPS.

Update - Slashdot has just posted a related article.

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