DNA - to freeze or not to freeze

[bficken]

When it comes to DRY DNA evidence (swabs, etc), I was always taught that it should go into the freezer to prevent degredation. My lab was recently told by our state DOJ that this was not necessary, and that such evidence could be stored on the shelf of our Property room as long as the room was temperature controlled.

How is everyone else handling this type of evidence? Freezer or standard storage? More importantly - does anyone know of recent research done on this topic? If my lab changes its procedures, we would need to back it up with published articles and references.

[sandra wiese]

It is my understanding that things like Sexual Assault kits and whatnot were refrigerated because there were blood tubes in them and those had to be refrigerated. Since our kits no longer have blood tubes in them (when taken they are submitted separately), the kits are stored on a shelf. It has been about 7 years since I worked in any capacity in a Property Unit, but it was longer than that when we stopped storing new kits and dry DNA evidence (swabs and blood cards and such) in the fridge or freezer. It is my understanding that the greatest detriment to DNA viability comes from fluctuations in temperature rather than the temperature itself (extreme high temps/UV exposure excluded) and with modern DNA techniques using ever smaller amounts, room temp storage is just fine. Bearing in mind of course, that room temperature in a main storage room where people work every day is generally considered a controlled temp environment but, say, an off-site storage facility where things are merely stored and temperatures can be extreme in both directions is not recommended.

I cannot point you to any studies, but I'm sure your DNA analysts can or should be able to. This is pretty "old" knowledge.

[bficken]

Thank you, Sandra. My current laboratory employs fingerprint experts only. So there were no DNA experts around to ask.

Two of us have previously worked for larger laboratories in the SF Bay Area that do employ DNA analysts. Both of those labs are still freezing their dry evidence. So I appreciate hearing from the world outside our bubble!