Page 1 of 1
mag powder and DNA
Posted: Thu Dec 26, 2013 9:18 am
by sandra wiese
After reading the synopses of several upcoming articles in the Identification News, it seems there is an issue with certain magnetic powders and DNA recovery. I can't seem to find much more information, although I am admittedly very far behind in my work-related reading. Can anyone bring us up to speed relatively quickly? Several of our CSI's use mag powder for everything they can and I would hate to find out later that they are prohibiting DNA recovery. Help?
Re: mag powder and DNA
Posted: Thu Dec 26, 2013 1:37 pm
by SConner
To the best of my knowledge and what has been communicated through the grapevine between our DNA analysts and those of us in the evidence processing unit, magnetic powder doesn't necessarily inhibit DNA recovery, it might make the sample a little dirtier or not as clean as they may like it for interpretation, but we still routinely swab after processing with any kind of powder not just magnetic and haven't been told to stop, yet. We do make sure to clean the wands before and after use and we use shaker jars to limit the potential for cross contamination between items/cases.
Re: mag powder and DNA
Posted: Sun Dec 29, 2013 9:04 am
by timbo
Mag powder has been shown by at least one study to significantly inhibit or even preclude subsequent DNA testing. See the article below:
Roux, C., Gill, K., Sutton, J. and Lennard, C. (1999). “A Further Study to Investigate the Effect of Fingerprint Enhancement Techniques on the DNA Analysis of Bloodstains”. Journal of Forensic Identification. 49 (4), pp. 357-376.
The effect on DNA testing may also depend on the DNA sampling and amplification methods, I'm not sure. Cotton swabbing and PCR were used in this study.
Use with care.......
Re: mag powder and DNA
Posted: Mon Jan 27, 2014 11:51 pm
by CamilleB
I have a question please regarding the transfer of touch DNA when using fiberglass or natural latent print brushes. I’ve collected the research articles I can find showing transfers can occur.
When touch DNA may be collected at a scene and single-use brushes are used, how often or when should the brushes be changed? (The same question with single-use powder.) Often I see phrasing that says “change gloves often” that is referenced to minimizing transfer contamination. Does anyone have more specific direction or written guidelines they use for use of brushes in these circumstances? (and powders?)
Thanks very much.