CLPEX Chat Board

Hello,

Our laboratory currently performs swabbing on evidence prior to latent print processing for the potential recovery of touch DNA. We are currently gathering some research on laboratory results on either re-swabbibng the evidence after processing, or solely collecting the swab after processing and the difference in DNA recovery. Does any labortaory have data on this type of procedure? Specifically if there is a difference in the percentage of cases where DNA was recovered by swabbing post-processing (success rates). I know that research has been down to show that CA fuming and dye-staining does not affect DNA, however the possible "washing away" of DNA material by dye-staining may be a consideration along with any potential contamination from shared laboratory equipment, etc. I would appreciate any thoughts or feedback.

Thanks,
Andrew Reitnauer
NYPD Police Laboratory

Hi Andrew,

Out here in San Diego if an item is calling for latent print development and DNA swabbing we will process the item (if it is non-porous) using superglue and powder, locate any latent prints, and then swab for DNA. We don't use anything like dye stain or VMD on the item if we know that DNA swabbing is going to be needed. If we are processing an item with a surface that is not condusive for latent prints, such as a gun grip, then we will swab that surface prior to any latent print development techniques. If the item is porous then we will process it using Ninhydrin prior to any DNA analysis. Although I don't have an exact percentage as far as our success rate using these methods I can tell you that we are very successful. I hope this helps.

Adam