Freezing Evidence


I manage a Police Department Property Evidence Division. We receive about 200 items a day from officers who seize evidence and prisoner's property ... Routinely these items (back packs, bags, etc.) have some type of food item attracting fruit flies. We have taken steps to mitigate the problem including requiring officers to bag everything they submit in plastic bags, bug lights and my least favored option of using insecticides in the warehouse through a commercial vendor. We have even been experimenting with freezing the little critters in our 15 below freezer which seems to deal with the living, but not the unborn.

This is a continuing problem/nuisance for us. You haven't lived until you pick-up a piece of property to return to a homeless person and a dozen fruit flies spring forth some of which fly into your mouth. I have been in the law enforcement business for appropaching three decades and this experience is one of the most disgusting.

I would appreciate any tips you can provide to help us contend with this on-going issue/problem.

- Multnomah County, OR
Fruit flies swarming backpack

From your description my guess is that fruit flies are not the only problem!

Freezing is by far your best option. Freezing will kill all stages of insects if you do it long enough. The time needed will depend on the size and density of the material but overnight is usually enough at least for insect collections (wood/glass boxes) that need to be treated. I'd experiment a little if you can and increase the time in the freezer as much as possible.

All other options will be more difficult and more potentially hazardous.

Jack DeAngelis
Extension Specialist (retired)
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