| 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. |
- Hedman, Johannes, et al.
(författare)
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Improved forensic DNA analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles
- 2009
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Ingår i: BIOTECHNIQUES. - : Eaton Publishing. - 0736-6205 .- 1940-9818. ; 47:5, s. 951-958
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Tidskriftsartikel (refereegranskat)abstract
- DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase-buffer systems can improve the quality of forensic DNA analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance forensic DNA analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.
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| 3. |
- Hedman, Johannes, et al.
(författare)
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Using the new Phadebas® Forensic Press test to find crime scene saliva stains suitable for DNA analysis
- 2008
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Ingår i: Forensic Science International: Genetics Supplement Series. - : Elsevier BV. - 1875-1768. ; 1:1, s. 430-432
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Tidskriftsartikel (refereegranskat)abstract
- The Phadebas® Forensic Press test is a new product that detects saliva stains by reacting with amylase. When the paper is pressed against a saliva stain a blue spot occurs. To test the sensitivity of the paper, a set of dilution series of saliva down to 1:500 was prepared on cotton fabric. Blue spots could be seen for dilutions of 1:100 when incubated at room temperature, and 1:200 in 37 °C. However, incubation at 37 °C did not provide acceptable reproducibility. The Phadebas® test was compared to four different lightsources for the ability to detect saliva on different carrier materials. Cotton fabric (T-shirt), denim, suede, leather, painted wood and untreated wood were tested. On denim, no stains could be detected with the lightsources, but Phadebas® showed all stains for pure saliva and dilution 1:5. DNA analysis was performed on detected stains and corresponding spots on the Phadebas® paper. Complete DNA profiles were produced for stains from pure saliva and dilution 1:5.
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