U.S. flag

An official website of the United States government, Department of Justice.

Preventing Hydrolytic and Oxidative Damage to Biological Evidence with Antioxidants and Chelators

NCJ Number
Date Published
December 2020
20 pages

This is the Final Summary Overview of the findings and methodology of a research project whose goal was to identify an effective method for long-term preservation of forensic DNA evidence by using commercial-off-the-shelf (COTS) preservatives that can be applied directly to evidence collection substrates.


The project examined the preservative effects of three chelators and four antioxidants on forensically relevant biological materials deposited on cotton swabs. Chelating agents and antioxidants interfere with DNA degradation caused by hydrolysis and oxidation. The chelating agents examined were desferrioxamine (DFOA), diethylenetriamine pentaacetic acid (DTPA), and ethylenediaminestetraacetic acid (EDTA). The antioxidants were alpha-tocopherol, astaxanthin, hydroxytyrosol, and zinc. Each of the preservatives tested has been shown to be an effective chelator and antioxidant in other applications. Phase 1 of the project examined the chelators and antioxidants for long-term functioning with biological materials deposited on cotton swabs and stored for varying time periods under a range of environmental conditions. In Phase II, six application methods for applying preservatives to swabs were evaluated. A total of 2,571 samples were prepared for Phase I. Following application of the biological samples, all swabs were dried at room temperature for about 1 hour. In Phase II, six methods for applying preservative solutions in a collection swab were evaluated. This study presents a novel method for preservation of evidence samples collected on swabs. Applications of EDTA solution to cotton swabs using metered dropper bottles, pretreated swabs, or moistened swabs does not require expensive instruments or specialized skills and can be easily adopted by any crime scene unit/investigator or crime laboratory regardless of funding level. Preserving biological evidence for potential long-term storage may aid in the prosecution of cold cases and the exoneration of innocent convicted persons due to DNA technology advances. 4 figures, 7 tables, and 17 references

Date Published: December 1, 2020