Dear Joe,

We keep getting more and more biological evidence submitted to the evidence room and I'm running out of freezer space. My boss wants to know if you had any recommendations for the best freezers to purchase for the storage of bio evidence

Thanks, Outa Freezer Space

Dear Outa Freezers Space

Maybe not! Things are changing and freezers may be a thing of the past. As we have crossed the country with all of our training classes, we have found that everyone has a different opinion about the necessity to freeze / refrigerate evidence.

The following are excerpts from the "The Biological Evidence Handbook: Best Practices for Evidence Handlers," and is used with the permission of the National Institute of Standards and Technology.

Biological Evidence Environmental Condition

The proper drying and packaging of biological evidence is the first step toward achieving optimal preservation. The next step is storing it in the proper environmental conditions. Biological evidence must be stored in a fashion that not only safeguards its integrity but also ensures its protection from degradation. The storage of biological evidence may include, but is not limited to, the use of temperature- and humidity-controlled areas or freezers and refrigerators.

Biological evidence should be stored in one of the following environments depending on the type of evidence, and if known, the type of analysis that will be conducted:

• Frozen: Laboratory freezer storage temperatures at or below -10°C (14°F)
• Refrigerated: Stored between 2°C (35°F) and 8°C (46°F) with less than 25% humidity
• Temperature Controlled: Stored between 15.5°C (60°F) and 24°C (75°F) with less than 60% humidity
• Room Temperature: No temperature or humidity control guidelines

The first table, Temporary Storage Conditions Matrix, provides guidance in the temporary storage of biological evidence, while the second table, Long Term Storage Conditions Matrix, is related to the long-term storage of bio evidence.     

 Temporary Storage Conditions Matrix

 Temporary Storage Conditions Matrix

 Glossary   (NOTE FROM JOE: THE BELOW DEFINITIONS ARE FROM THE HANDBOOK GLOSSARY).

This glossary is provided as a guide in the interpretation and understanding of the document. When possible, definitions were selected from existing references. Certain definitions were specifically crafted to elucidate the intent of the document.

Biological Evidence: Biological material recovered from crime scenes commonly appear in the form of hair, tissue, bones, teeth, blood, semen, or other bodily fluids. Biological evidence refers to samples of biological materials or evidence items containing biological material.

Biohazards: Materials that contain blood or other potentially infectious materials. These materials include many of those found in biological evidence including: semen, vaginal secretions or any body fluid that is visibly contaminated with blood, and all body fluids in situations where it is difficult or impossible to differentiate between body fluids as well as any unfixed tissue or organ from a human (living or dead) that can be collected at a crime scene and stored. (Occupational Safety & Health Administration, 2011)

However, requiring the retention of all physical evidence that can potentially contain DNA would result in the retention of all evidence collected unless it was screened to determine the possible presence of genetic material. Therefore, our recommendations attempt to balance the interests of justice with practicable storage concerns and offer a minimum threshold for biological evidence retention. The table below describes different types of evidence that can contain biological evidence which in turn, could be tested for DNA

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Examples of Sources of Biological Evidence

(National Institute of Justice, 2003)

 Regards,        

Joe Latta  Executive Director