|Posted on Thursday, April 28, 2005 - 04:10 am: ||
You did not indicate that the surface was soot-covered, thus it does not seem that you experienced the removal of various layers of soot by sequential "lifting" to expose underlying prints that were previously invisible.
With the assumption that your evidence was safeguarded so as to preclude a coworker or janitor from inadvertently adding new latent prints between dusting steps, my guess is that you experienced prints developed by "powder rubbing," prints which were not visible via normal dusting with a brush. The additional evidence handling (and perhaps the additional brushing above and beyond what you normally do) could have been enough to mimic the powder rubbing technique discovered by Virginia State Crime Lab LP Examiners over 20 years ago.
Mike Grimm and Dick Taylor's article "Super Glue Sticks it to the Bad Guys" (Identification News, March 1984, pages 7-11) details how after conventional dusting with brush and powder, further handling of evidence "accidentally" caused previously invisible latent prints to appear.
As mentioned several times before on this forum, when dusting with brush and powder you are going after latent prints that are somewhat sticky. Faint latent prints developed in superglue fumes on a smooth nonporous surface can be three dimensional without being sticky... thus you are going to miss those prints if you merely cyano fume and dust with a brush. Powder rubbing causes a build-up of powder on both sides of three dimensional ridge detail developed in superglue (polymerization) deposits and often times such ridge detail has reverse color ridges (the powder fills in the furrows).
Even if you are diligent about fuming, dye staining, and dusting nonporous surfaces, you should always use powder rubbing (with a contrasting color powder) as the last technique before you have finished with nonporous evidence. Otherwise, you will miss identifiable latent prints that are present but not "sticky" and which were too faint or may have been otherwise obscured by competing background fluorescence (noise) during the dye staining and luminescence exam steps.
|Posted on Wednesday, April 27, 2005 - 03:29 pm: ||
I am requesting information as to if anyone out there in the latent print field has come across a time when they have processed a piece of evidence and lifted two different latent fingerprints on top of each other, and I don't mean a cross section or overlaying latents. This was an arson case I am working and I started by processing with superglue and lifting with white powder and then after using white powder I used black powder. On the fourth lift I had a completely different fingerprint. If you have come across something like this please let me know.