Factors affecting DNA recovery from cartridge cases

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Factors affecting DNA recovery from cartridge cases. / Jansson, Linda; Forsberg, Christina; Akel, Yasmine; Dufva, Charlotte; Ansell, Carina; Ansell, Ricky; Hedman, Johannes.

I: Forensic Science International: Genetics, Vol. 48, 102343, 2020.

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Jansson, Linda ; Forsberg, Christina ; Akel, Yasmine ; Dufva, Charlotte ; Ansell, Carina ; Ansell, Ricky ; Hedman, Johannes. / Factors affecting DNA recovery from cartridge cases. I: Forensic Science International: Genetics. 2020 ; Vol. 48.

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TY - JOUR

T1 - Factors affecting DNA recovery from cartridge cases

AU - Jansson, Linda

AU - Forsberg, Christina

AU - Akel, Yasmine

AU - Dufva, Charlotte

AU - Ansell, Carina

AU - Ansell, Ricky

AU - Hedman, Johannes

PY - 2020

Y1 - 2020

N2 - Cartridge cases are often the sole items left behind after a shooting incident and DNA traces from these can identify persons connected to the shooting. However, the chance of retrieving usable DNA profiles from cartridge cases is limited, due to the low amounts of deposited DNA and subsequent DNA loss associated with the firing process. In the current study, we set out to increase the DNA recovery from cartridge cases and cartridges by evaluating different swab types and detergents used for trace collection. A protocol applying nylon-flocked swabs instead of cotton swabs was implemented in casework at the Swedish National Forensic Centre (NFC), increasing DNA yield. The number of samples providing a DNA concentration ≥ 0.001 ng/μL (the in-house cut-off for processing low-template samples) increased from 11.1 to 28.6 % for cartridge cases and from 16.0 to 43.3 % for cartridges. There was also a substantial increase in mixed STR profiles, too complex to use for comparisons. Thus, it was not possible to take the full advantage of the elevated DNA yield provided by nylon-flocked swabs. The number of usable STR profiles increased from 5.0 to 8.0 % for cartridge cases and remained unchanged for cartridges. Controlled studies were performed to assess the impact on the DNA recovery from different persons handling the ammunition, different material and size of the cartridge cases, and the type of firearm used. These studies reflected an ideal situation, where all cartridges were extensively handled and loaded without gloves, thus providing a higher expected DNA yield compared to most casework samples. The total peak height differed by up to a factor of ∼50 when 20 different persons handled cartridges prior to shooting. By evaluating eleven combinations of different firearms and ammunition, it was found that the casing material and type of firearm also have a substantial impact on DNA yield.

AB - Cartridge cases are often the sole items left behind after a shooting incident and DNA traces from these can identify persons connected to the shooting. However, the chance of retrieving usable DNA profiles from cartridge cases is limited, due to the low amounts of deposited DNA and subsequent DNA loss associated with the firing process. In the current study, we set out to increase the DNA recovery from cartridge cases and cartridges by evaluating different swab types and detergents used for trace collection. A protocol applying nylon-flocked swabs instead of cotton swabs was implemented in casework at the Swedish National Forensic Centre (NFC), increasing DNA yield. The number of samples providing a DNA concentration ≥ 0.001 ng/μL (the in-house cut-off for processing low-template samples) increased from 11.1 to 28.6 % for cartridge cases and from 16.0 to 43.3 % for cartridges. There was also a substantial increase in mixed STR profiles, too complex to use for comparisons. Thus, it was not possible to take the full advantage of the elevated DNA yield provided by nylon-flocked swabs. The number of usable STR profiles increased from 5.0 to 8.0 % for cartridge cases and remained unchanged for cartridges. Controlled studies were performed to assess the impact on the DNA recovery from different persons handling the ammunition, different material and size of the cartridge cases, and the type of firearm used. These studies reflected an ideal situation, where all cartridges were extensively handled and loaded without gloves, thus providing a higher expected DNA yield compared to most casework samples. The total peak height differed by up to a factor of ∼50 when 20 different persons handled cartridges prior to shooting. By evaluating eleven combinations of different firearms and ammunition, it was found that the casing material and type of firearm also have a substantial impact on DNA yield.

KW - Ammunition

KW - Crime scene

KW - Firearms

KW - Nylon-flocked swab

KW - Short tandem repeats

KW - Trace DNA

U2 - 10.1016/j.fsigen.2020.102343

DO - 10.1016/j.fsigen.2020.102343

M3 - Article

C2 - 32683317

AN - SCOPUS:85087951773

VL - 48

JO - Forensic Science International: Genetics

JF - Forensic Science International: Genetics

SN - 1878-0326

M1 - 102343

ER -