Post Number: 231
|Posted on Monday, June 25, 2007 - 06:01 am: ||
Reverse color ridge detail, where dark-colored fingerprint powder adheres to the background instead of the ridge detail, can be caused by the "lifting away" of a contaminate present on a surface (such as gun oil) during contact with friction ridge skin of the fingers or palms. Thereafter, "dusting" with dark-colored fingerprint powder may visualize reverse color impressions (dark furrows and lighter-colored ridges).
Other factors can also create such an appearance, such as a contaminate on the finger/palm (e.g., blood, oil, or body fluids) transferred to the surface touched. Presssure from the contact can cause a squeegee effect where the contaminate is pressed away from the ridges and left deposited on the surface primarily in the configuration of the furrows.
It is not unusual for only part of a latent finger or palm print to be reverse color, and the remainder normal color (part of the print has ridges the opposite color of the remainder of the print's ridges). Reverse color also occurs when ink used in recording finger and palm prints is too runny (such as the ink a seldom used porelon fingerprinting pad, especially in high temperatures). Sweat or other liquid on fingers and palms can also sometimes contribute to partially reversed color live scan impressions.
This phenomenon (reverse color) is one of the reasons why many automated fingerprint identification systems treat ridge endings and bifurcations in a similar manner (i.e., a ridge ending in reverse color may appear to be a y-shaped formation [birfurcation]).
Martin Snook (Printman44)
Post Number: 2
|Posted on Thursday, June 21, 2007 - 02:55 pm: ||
I should have clarified my statement. This is reference to reverse color. Valley's appear black, and ridges appear white.
Michele Triplett (Michele_triplett)
Post Number: 12
|Posted on Thursday, June 07, 2007 - 10:19 am: ||
Was it identified to the person who lifted the print?
Usually reversed prints refer to the direction of the print. It ususally indicates that the latent was either transfered to the item or was left on the tape (and not actually on the object that was being processed).
There's also another type of reversal that's known as a tonally reversed print. This doesn't mean the print is in the reversed position, it means that when an item was touched that ridges appear the opposite color than you'd expect them too. For example, if you were processing something with black powder you'd expect the ridges of the latent print to show up in black. Most of the time this is true but once in a while the ridges show up as white and the furrows are black. There are several reasons for this but it usually occurs due to pressure or moisture. Stating that there is a tonal reversal doesn't mean the ID is harder, it's usually just a note.
In your case, I think you have to find out how this examiner is using the term (reversed image or tonally reversed image) before you can speculate further.
Martin Snook (Printman44)
Post Number: 1
|Posted on Wednesday, June 06, 2007 - 01:44 pm: ||
Can someone give me their explaination of a latent print that appears as a reverse image? The latent was collected from a gun scope. It was processed with black powder, lifted with standard lifting tape, and applied to a standard lift card. When viewing the latent, it appears as a reverse image.