Friday, May 30, 2014

A Forensic Hole In Ontario

I have a habit of noticing things, and then questioning what I just saw.  This then generally leads me on a series of questions as I dig deeper into “why” something happened, and why that thing happened, and the cause of the thing that made the thing happen that caused the thing I noticed.

One such area where this happens is electricity.  

As a kid, I used to notice the lights dim briefly every evening on weekdays at about the same time each day.  This turned out to be a result of grid switching some 40 miles away from me.  The reason for the switching was to bring on extra power to cope with the evening demand as people came home and cooked and switched on the television for the night.  As an adult, I still notice things like this - though these days, it’s a little more complicated as to what’s going on because now I live in Toronto, where we have many more factors to consider, but I still notice when the electricity supply changes.  What many people don’t know is that in addition to these big changes that are easily perceptible by dimming lights, or a drop in the tone of the noise from your furnace fan or hairdryer, there’s smaller changes happening.  

Without going into the specifics of generation and transmission mechanics, the grid has small changes happening all the time and it affects everything from the brightness of your lights, to the hum of your air conditioning.  This changing hum is known as the Electric Network Frequency.  

The amazing thing about it is it’s a unique pattern - if you record the frequency at regular intervals on the power grid, you can then match it to the hum found on audio tracks in a video or the brightness of lighting and determine what time that video was filmed.  This is called Electrical Network Frequency (ENF) analysis.  In some countries, it is now being regularly used to determine the time that crimes happened.  

A while ago, the question that crossed my mind was “who in Ontario records this frequency to help criminal investigations in here?”.   I asked everyone from the generator to the distributor to the regulator, and nobody claims to keep a record of the frequency.

If that’s true, then that’s a shame.  From a forensic standpoint, this is a really good tool that have, and Ontario at least doesn’t have access to it.