When you talk about digital evidence there are a few variables you need to consider:

  • Number of cameras (discussed in previous post)
  • Resolution (discussed in previous post)
  • Hours of video per car
  • Hours of video per officer
  • Non-evidence retention period
  • Evidence rate and retention period

We have worked with a number of different law enforcement agencies and service providers and here are the averages we have seen for the variables:

  • Hours video per car per day: 6 (includes multiple shifts)
  • Hours of video per officer per day: 2-6
  • Non-evidence retention period: 30-90 days
  • Evidence rate and retention period: 10% at 3-7 years (sometimes forever)

Now let’s create a model based off of a medium-sized department of 320 sworn with 135 vehicles (around the size of Cleveland, Ohio) and use two in-car cameras at 1 GB/hour and 0.5 GB/hour, two 720 HD body worn video (BWV), 10% evidence and 90 day retention.

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You can see at the end of year 5 this agency will have over one petabyte of storage under management. Now if you add just one 1080HD camera to the mix it doubles these figures! As previously discussed, resolutions will always go up. All agencies will ultimately be capturing 1080HD resolution – it’s only a matter of time.

Screen Shot 2015-05-28 at 2.15.46 PM

How evidence is like revolving debt

Now there are two interesting things to point out. The first is in what the larger storage capacities of body worn cameras result in. That really is a factor of new technology; there are in-car cameras that can capture higher resolutions, but I wanted to present a realistic model. What really sets off the overall capacity is the compounding effect of evidence. You can see in year 3, evidence overtakes non-evidence from a capacity perspective. As resolutions go up, number of cameras increases, and sources of digital evidence increase (audio, mobile, photos), these numbers will continue to increase and retention rates and our litigious society will ensure the compounding effect is preserved.

If you manage IT in law enforcement today are you looking at that petabyte figure and wondering how you can get there? The bad news is it will be really expensive with your current NAS/SAN and JBODs will be very difficult to manage and upgrade. The good news is that you can easily get there with object storage but there are other considerations that I will explore in the next post.