| 1. |
- Dufva, Charlotte, et al.
(författare)
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DNA profiles obtained from urine in snow
- 2019
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Ingår i: Forensic Science International. - : ELSEVIER IRELAND LTD. - 1875-1768 .- 1875-175X. ; 7:1, s. 544-545
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Tidskriftsartikel (refereegranskat)abstract
- Urine can be a potential important source of evidence when occurring at crime scenes. In case of outdoor scenes including snow a yellow colour could indicate the existence of human urine. In an effort to be able to investigate urine as a crime scene sample we have evaluated protocols for analysing DNA from urine in snow. Two different tests were performed with a smaller and a larger volume of urine dispensed on snow. The tubes were put into a freezer to mimic winter conditions. A Urine Preservative was added to some of the samples. DNA profiles were compared between samples extracted using a Urine DNA Isolation Kit and samples extracted with a Chelex-based method. In addition, a test was performed with the aim to mimic a potential crime scene. With a smaller volume of urine the best quality DNA profiles were obtained using the Urine DNA Isolation Kit without the Urine Preservative. When a larger volume of urine was handled and in the crime scene setup, there were no clear difference between the two extraction methods. Instead, the variation observed was between individuals.
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| 2. |
- Hedman, Johannes, et al.
(författare)
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Synergy between DNA polymerases increases polymerase chain reaction inhibitor tolerance in forensic DNA analysis
- 2010
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Ingår i: Analytical Biochemistry. - - : Elsevier Inc.. - 0003-2697 .- 1096-0309. ; 405, s. 192-200
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Tidskriftsartikel (refereegranskat)abstract
- The success rate of diagnostic polymerase chain reaction (PCR) analysis is lowered by inhibitory substancespresent in the samples. Recently, we showed that tolerance to PCR inhibitors in crime scene salivastains can be improved by replacing the standard DNA polymerase AmpliTaq Gold with alternative DNApolymerase–buffer systems (Hedman et al., BioTechniques 47 (2009) 951–958). Here we show thatblending inhibitor-resistant DNA polymerase–buffer systems further increases the success rate of PCRfor various types of real crime scene samples showing inhibition. For 34 of 42 ‘‘inhibited” crime scenestains, the DNA profile quality was significantly improved using a DNA polymerase blend of ExTaq HotStart and PicoMaxx High Fidelity compared with AmpliTaq Gold. The significance of the results was confirmedby analysis of variance. The blend performed as well as, or better than, the alternative DNA polymerasesused separately for all tested sample types. When used separately, the performance of the DNApolymerases varied depending on the nature of the sample. The superiority of the blend is discussed interms of complementary effects and synergy between the DNA polymerase–buffer systems.
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| 3. |
- Jansson, Linda, et al.
(författare)
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Factors affecting DNA recovery from cartridge cases
- 2020
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Ingår i: Forensic Science International: Genetics. - : Elsevier BV. - 1872-4973 .- 1878-0326. ; 48
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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