Does anyone here have a good source for understanding how long touch dna can stay on brass specifically?
I've found several studies (links below) that talk about how brass and copper are the most difficult metals to recover touch dna from. However , I can't find any that discuss how long it stays on. There are studies comparing cotton and stainless steel, and stainless steel is excellent at keeping touch dna for a very long time. But due to the copper ions, touch dna on brass would degrade much faster than on steel. I can't find an answer as to how fast exactly.
Obviously the relevance of this is to try to understand what the realistic window is when BK could have left the touch DNA on the kabar button snap. The fact that the snap is brass, not aluminum or steel, is the challenging factor. Is it hours? Days? Weeks?
The shorter the window, the more difficult it would be for BK to explain away. However, if the window is too small and touch DNA on brass degrades within say, 12 hours, then there is a problem.
Brass issues:
And
Cotton and Stainless steel: