| 1. |
- Hedman, Johannes, et al.
(författare)
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A fast analysis system for forensic DNA reference samples
- 2008
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Ingår i: Forensic Science International: Genetics. - : Elsevier BV. - 1878-0326 .- 1872-4973. ; 2:3, s. 184-189
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Tidskriftsartikel (refereegranskat)abstract
- On January 1st, 2006, the Swedish legislation on obtaining DNA reference samples from Suspects and the recording of DNA profiles in databases was changed. As a result the number of samples analysed at the Swedish National Laboratory of Forensic Science (SKL) increased from about 4500 in 2005 to more than 25,000 in 2006. To meet this challenge, SKL launched a flew analysis system to create an unbroken chain, from sampling to incorporation of a profile in the national DNA database and subsequent automatic generation of digitally signed hit reports. The system integrates logistics, digital data transfer, new functions in LIMS (ForumDNA Version 4, Ida Infront AB) and laboratory automation. Buccal swab samples are secured on a FTA (R) card attached to an identity form, which is barcoded with a unique sample ID. After sampling, the police officer sends a digital request to SKL. The sample is automatically registered in LIMS and processed on delivery. The resulting DNA profiles are automatically classified according to quality using a custom-made expert system. Building the evaluation around mathematical rules makes it reproducible, standardised and minimises manual work and clerk errors. All samples are run in duplicate and the two profiles are compared within LIMS before incorporation in the database. In the first year of operation, the median time for completion of an analysis was 3 days, measured from delivery of the sample to incorporation of the profile in the national DNA database. In spite of the dramatic increase in the number of reference samples there was no backlog. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
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| 2. |
- 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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| 3. |
- Forsberg, Christina, et al.
(författare)
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The need for automation is limited when using a quick and inexpensive one-tube DNA extraction protocol for crime scene samples
- 2019
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Ingår i: Forensic Science International: Genetics Supplement Series. - : Elsevier BV. - 1875-1768. ; 7:1, s. 377-378
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Tidskriftsartikel (refereegranskat)abstract
- Generally, simplified manual protocols can serve as a cost-effective alternative to sophisticated automation solutions. We have developed, validated and implemented a quick, inexpensive and efficient one-tube direct lysis DNA extraction protocol for the majority of our crime scene samples. The method includes one pipetting step, the addition of a lysis buffer based on Chelex beads, Proteinase K and Tween 20. After three incubation steps with vortexing in between, the sample is ready for downstream applications (DNA quantification and STR profiling). The amount of lysis buffer added varies between 200–1000 μL depending on the amount of carrier material in the tube. If needed the extract can be purified or concentrated using a filter device, in our case Amicon Ultra-2. Through in-house validation we show that the method is fit-for-purpose for application in casework for samples containing blood, saliva, shed cells and semen as it provides high DNA yields and high quality STR profiles. The method was implemented at the Swedish National Forensic Centre (NFC) in February 2018. During the first year more than 35,000 crime scene samples were extracted using the method, generating DNA yields equivalent to the previously used method. In conclusion, the need for automation of the DNA extraction process is limited when using a one-tube direct lysis protocol including only the addition of lysis buffer and no transferring steps. In addition it saves costs as there is no need for expensive pipetting robots or service fees and since the reagents used in this direct lysis protocol are relatively inexpensive.
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