Tuesday, March 31, 2020

An improved process for the collection and DNA analysis of fired cartridge cases

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Michael Whyte
Crime Scene Officer and Fingerprint Expert with over 12 years experience in Crime Scene Investigation and Latent Print Analysis. The opinions or assertions contained on this site are the private views of the author and are not to be construed as those of any professional organisation or policing body.
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Improvements to the DNA analysis of fired cartridge cases have been made in recent years, yet successful analysis of this important evidence type remains difficult.

A study published recently in Forensic Science International: Genetics, describes both a novel device for the collection and transport of fired cartridge cases and a new DNA recovery method that incorporates a rinse-and-swab technique.

This technique combines two different types of swabs and a rinse solution with additives that reduce the degradative effects that copper has on DNA. Studies suggest that copper may inhibit downstream PCR and/or degrade DNA through oxidative damage. It is hypothesized that DNA damage is the result of oxidative stress from free radicals due to the reduction of transition metals (i.e. copper). 

The researchers developed a new DNA recovery method, along with a series of rinsing and swabbing steps to reduce the deleterious effects of copper contained in brass cartridge cases and to maximize the recovery of DNA.

The new recovery method yielded approximately threefold more DNA than the traditional double swab method and reduced the evidence of degradation. 

The researchers then tested this new method on real case work applications by testing over 100 cartridge cases collected from crime scenes. Approximately 67% of the time (8 of 12), at least one DNA profile suitable for comparison was obtained from fired cartridge cases assumed to be associated with a single firearm using the collection device and the rinse-and-swab method when the fired cartridge cases were collected within 24 hours.

To learn more about this study and the new DNA recovery method;

Read the Paper here

An improved process for the collection and DNA analysis of fired cartridge cases, Forensic Science International: Genetics, https://doi.org/10.1016/j.fsigen.2020.102238

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