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samarkandy

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Reply with quote  #1 
I have to thank poster Mama for unearthing and drawing my attention to this paper published in 1999 in the Journal of Forensic Science. It is one of the few papers that outlines details of the methods used and raw data obtained from their experiments, unlike so many other papers on Secondary DNA Transfer.

"A Systematic Analysis of Secondary DNA Transfer, November 1999 Carll Ladd,1 Ph.D; Michael S. Adamowicz,1 Ph.D.; Michael T. Bourke,1 Ph.D.;Carol A. Scherczinger,1 Ph.D.; and Henry C. Lee,1,2 Ph.D.

 

The concluding statement from the article:

"Our data do not support the conclusion that secondary transfer will compromise DNA typing results under typical forensic conditions."

https://projects.nfstc.org/workshops/resources/literature/Amplification/11_A%20Systematic%20Analysis%20of%20Secondary%20DNA.pdf


The kits used to amplify and type the DNA in these experiments were the AmpFlSTR Profiler Plus 􏰐and the COfiler DNA typing kits. The Profiler Plus kit types the alleles at 9 of the CODIS required loci. The COfiler types the alleles at an additional 6 loci. 

It was the AmpFlSTR Profiler Plus 􏰐kit that was used by CBI to generate the original 9 marker profile from the panties, which CBI achieved somewhere between 1997 and 1999, before Denver Police Forensics continued with and completed the testing in 2003 that resulted in generating that extra tenth marker that made the profile eligible for acceptance into CODIS.

Many people like to think that the DNA profile found in the panties bloodstain could have been due to touch DNA from secondary transfer. However, this idea is not at all realistic because secondary deposits of touch DNA result in such small amounts of DNA being left on the surface that they are below the levels of detectability of the test system.

The AmpFlSTR Profiler Plus 􏰐kit that was used by CBI required as much as 1.0 to 2.5 nanograms of DNA to test

http://tools.thermofisher.com/content/sfs/manuals/cms_040971.pdf
page 1.9 introduction 

If amounts tested are lower than the minimum the results would not be reliable. So it has to be assumed that even after CBA and Cellmark had used up so much of the bloodspot DNA for the earlier DQA1/PM and D1S80 tests back in 1997, there was still at least 1 nanogram left for CBI to start doing the AmpFlSTR Profiler Plus test.

This is more than any touch DNA amount left by secondary touch transfer has ever been reported.

Touch DNA deposited by secondary transfer to the bloodstained areas of the panties was not possible


 

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