Rubber Lifters

[Michele]

I just took a class on collecting impression evidence (all kinds of evidence). In the class they said that rubber lifters are porous and absorb the dust or powder and the lifted image will fade with time. They said that images should be photographed immediately after lifting.

Rubber doesn’t seem absorbent to me. I know there’s a thin layer of gelatin on the rubber that acts as an adhesive (or so I’ve read). This could be absorbent, but if it were, wouldn’t the adhesive on lift tape also have this same absorbent quality?

When I returned to work, I tried to look up information. I found that photography was recommended but it didn’t say that it was recommended because of fading. It appears to me that photography is recommended as a way to enhance the image or to reverse the image for easier comparisons.

If it’s true that latent prints fade on rubber lifters, could someone point me in the direction of an article or a research project that talks more about this? I think that if latents lifted with rubber lifters need to be photographed then why use the rubber lifter? Wouldn’t it be easier to just photograph the print before lifting it (or instead of lifting it)?

Thanks,

[Ernie Hamm]

Michele,

I do not believe this phenomenon has ever been documented. It seem to occur (on occasions) with the lighter powders (gray and white) and with the black lifters. No idea which combination of powder and lifter manufacturers was involved or if there was any relationship. I would believe the thickness of rubber lifters, as opposed to tape material, could contribute to an absorption property.

Ernie

[Gerald Clough]

Sounds like a huge overabundance of caution. I suppose no natural latex material can be considered structurally permanent, but that's a different issue. I wonder if this somehow was a notion that refers more to a very useful property of the BVDA Gelifters ("linen rubber" backing coated with gelatin with food-grade preservative), lifting of untreated impressions that are preserved entirely by disrupting the mirror-like gelatin surface. I don't have any cite for or experience of such impressions being lost over time, but I guess I have to suppose that under some conditions, the gelatin could swell. But as they pretty much have to be photographed using carefully arranged lighting to image the disruption, I wouldn't consider it a problem, or at least not one you could do anything else about.

[Kathy Saviers]

The benefits of a Rubber-Gelatin lifter are its low adhesiveness, color contrast and flexibility for use on contoured surfaces. Its low adhesiveness allows for use on paper items without tearing them. The color contrast allows for seeing the image, whether it is a latent print or footwear impression, on a higher contrast background than the original surface background. Say someone kicks in a door to gain entry and you can, sort of, see the footwear impression in light dust on the light wood-grain door. It is almost impossible to get a good photograph of it. Or, the same someone steps on some newspaper, leaving another light colored dusty print. Getting a good photograph of the impression minus the inked words and ads would be impossible. With a black Rubber-Gelatin lifter, you can recover the light colored footwear impression and now, easily photograph it against the black surface. The flexibility aspect is good for textured surfaces whether lifting a latent print or a footwear impression.

As to the image disappearing, I don't have any research data but some people have told me it has happened to them. As I remember from discussing this with the manufacturer years ago, he explained the adhesive portion of the lifter is a gelatin used in food production. I cannot remember if it was a preservative or what its function was, but he did warn that the dusty image can be absorbed and "disappear."

Along a new line, I remember people telling me that they have somehow washed the lifters after the case was done and used them again. I don't have any details on that process.

Kathy

[Cindy Rennie]

When I read the title of this message, I thought it was about people who were shoplifting condoms.

Coffee. I need more coffee.

[Patrick]

Dear Michelle,

This is what the manual says about this:

"To the best of our knowledge, there is only one case where a powdered fingerprint will fade on a BVDA Gellifter. This is where BVDA gold powder is used (Patrick: this is a fingerprint powder containing brass powder (copper/zinc alloy)). Lifted prints will fade and ultimately disappear in time. Fading will be noticeable after days or weeks, depending on the storage temperature (the lower the better). Prints developed with silver powders (aluminium), on the other hand, are known to have been stored for several years without apparent fading. However, we always recommend photographing prints as soon as possible."

and

"Lifted shoeprints (dust marks) may slowly fade in time. For very weak prints this may be noticeable after storing them for a few days. This will depend on the temperature. The lower the temperature, the slower they will fade. This, however, should not be a concern, since lifted shoeprints can easily be photographed after removing the cover sheet. Oblique lighting will show details which are not visible before photography. So far, we know of no materials that fade on the Gellifter surface before adequate photographs have been taken."

We recommend photographing the prints as soon as possible, no 'immediately'. Photography is
indeed needed as you will always have to flip the image to get in the correct position, in case of a black lifter, to invert the image so that you have a black fingerprint on a white background, to get the print on the lifter into AFIS and, if needed, to enhance the print. As a reward for making these efforts you will end up with the best possible image of the print!

Over the last couple of year's I have visited a lot of labs for demonstrations with our imaging system for Gellifters, the GLScan. During the demonstrations we always scan actual case work as well that the audience has available. Most of the time they will not give you the easiest lifts and quite often they the lifts are a few years old. As far as I remember we have always been able to image the prints on these lifts, even after the lifters were stored for a few years.

One thing that will make you think that your print has faded is actually not fading but diluting. This diluting of the print is caused by repeatedly replacing and removing the transparent cover sheet. Part of the dust print will stick to cover sheet and will be removed from the actual lifting surface when the cover sheet is removed.

That's why the following is recommended in the manual as well:

"For best results you should not replace the cover sheet. Transportation of the lifted print is of course more difficult then. We suggest using double-sided adhesive tape and a clean, shallow cardboard box, like the ones that photographic paper comes in."
The Home Office Scientific Development Branch in the UK has done research about this and published the results in their Fingerprint and Footwear newsletter. This is the link to their website where the news letter can be read/downloaded:

http://scienceandresearch.homeoffice.go ... iew=Binary

Kathy mentions in her reply that she heard of people washing the Gellifters after the case was done and then used them again. I don't think it is wise to reuse Gellifters, think about issues related to contamination. As importantly, a Gellifter used for a second time will never give an image a good as when it came from the package for the first time.

The quality of the image of a print on a black Gellifter heavily relies on the deep black color of the gelatin surface and on its mirror like surface. A part of the light used during photography is absorbed by the deep black color and a larger part is reflected by the glossy surface.
Where there is no trace material on the Gellifter the light is reflected in the same angle as it hits the surface (specular reflection). This light will not reach the camera and the camera will record this as black. Where there is trace material on the black surface, the light will be reflected in many directions (diffuse reflection) and will also reach the camera which will record this as grey to white color. This is even the case when you have black fingerprint powder on a black Gellifter, black powder contrasts perfectly on the black surface of the Gellifter.

If the surface of a Gellifter is cleaned, the surface will no longer be glossy. When you then photograph the lifter, the whole surface will diffusely reflect the light and the lifted print will not, or very poorly, contrast against the background.

I hope this helps. Please let me know in case further questions arise.

Best regards,

Patrick

[areitnau]

The only other instance I have heard of involving the fading of an impression on a gel lifter involves the lifting of a print developed with Acid Yellow 7, which is obviously a much different circumstance than a powder/lift situation...

Andy

[Patrick]

What Andy says is correct. Lifting blood prints which are stained with Acid Yellow 7, Hungarian Red, Amido Black etc. will start to fade shortly after lifting. Imaging these lifts immediately after lifting is highly recommended. What happens is that the stain in the blood print is dissolved by the glycerin in the gelatin layer and absorbed by the layer , it is not something that sticks to the gelatin layer like dust or fingerprint powder.

Patrick

[Neville]

Hi there
In NZ we use BVDA transparent fingerprint Gelifters, prints in dust definitely do disappear I have seen it happen on a number of occasions, and within a shift. I will always photograph the print even if I lift it. Strangely though I have not seen this occur with the BVDA black shoe lifters, well that I can remember anyway.

[David L. Grieve]

Michele, the instructors may have confused gel lifters and rubber lifters. Real, old fashioned rubber lifters replied upon the characteristics of natural rubber which is sticky but of low tack. Natural rubber is not porous. Gel lifters have the thin, gelatin coating, and while lower in tack than tapes, the gelatin is porous. Yes, I have seen white powder prints fade and disappear in gel lifters. I have never noted black powder absorbed in gelatin, but this may be due to a larger particle size.

White powder from certain suppliers was notorious for dissolving into the adhesive of some lifters, although the rate of loss varied according to other factors. I regularly saw this happen with tapes and gel lifters, but not with true rubber lifters. We warned agencies about the situation and since we had not witnessed fading with black powder, we recommended restricting the use of white powder or eliminating it. That didn't happen.

[Pat A. Wertheim]

Hi Dave

As I'm sure you remember, the original rubber lifters were tire patches.

In the 1943 murder of Sir Harry Oakes, Capt. James Otto Barker of the Miami Police Department used a white rubber bicycle patch to lift a latent fingerprint identified to Alfred de Marigny. Barker introduced a photograph of that lift in court, but the original lift was never produced. The defense proved it could not have come from the surface Barker claimed and de Marigny was acquitted. For a great true crime read, find a copy of "Conspiracy of Crowns" by Alfred de Marigny. For a great "Rest of the Story" read, find Dave Grieve's editorial "Long Road to Deadwood" about the 1944 IAI Conference at which Barker's alleged fabrication of evidence was the primary topic.

Does anybody still carry white rubber bicycle tire patches in their kits?

[David L. Grieve]

Hi, Pat.

Of course I remember tire patches, needed when tires all had tubes. And every car carried a tire pump. One of the men who trained me was a sworn officer who everytime he got mad, he threatened to transfer back to the street. Then he would laugh and say the only thing he remembered about patrol was not to put his foot on the running board when writing a ticket. To borrow from another thread, Kathy Saviers may have dated Henry but she didn't know he was my younger brother.

[gerritvolckeryck]

I'm a blackgel addict (and therefor a good friend of Patrick). I agree with what he wrote (and Kathy and David). We have had our problems of dissapearing marks (and still have), but as long as you know how and when it happens, you can anticipate.

Gel = water
everything that is water soluble will eventually dissolve into the gel.

Some years ago, a few elderly collegues went bereserk because the gellifters "ate" their fingerprints in a matter of days. They mentionned that they still kept their little jar of "lead carbonate" (white powder) for "special cases". Lead carbonate is water soluble and thus - in combination with gellifters - a disaster.

A simple test is to put some of your fingerprint powder into a small amount of water. Shake it and you'll soon notice if (part of) it is water soluble.

Dust ? You can only guess what it consists of, so it might dissapear in time.

Just one more thing to try : put your fingers on a more or less clean surface. Lift the marks with a black gel without using any other enhancement technique. If you're a good photographer (or if you use the GLScan), you'll get better results than if you had dusted them.

All the best,

Gerrit
http://www.sptm.be

[Ernie Hamm]

Okay, I needed to dig through my retired and boxed library to check on ‘rubber lifters’. Bob Olsen in “Scott’s Fingerprint Mechanics” (1978) states on page 381, “Adhesive substances on all types of lifters sometimes absorb or obscure light-colored fingerprint powders.”

So, I then checked Walter R. Scott’s “Fingerprint Mechanics” (from whilst Bob got his title for his revision of the classic work, BTW: Bob loved using the term ‘whilst’). On page 196 of “Fingerprint Mechanics” (1951), it is stated, “Adhesive substances on tire patches, like cellophane tape, will obscure some kinds of light colored powders; the rubber cement has the effect of dissolving the image so far as visibility is concerned.” An additional entry on this page, “The tire patch is described here because it was the first lifting device.”

Michelle, no documentation on the phenomenon. Bob was undoubtedly citing Scott, but Scott gave no direct reference to his statement which probably came from his experience.

These observations were made long before the introduction of the gelatin type lifters, which have presented their own concerns as noted in some of the postings.

[fingerprint]

As far as I have been told/experienced, the story about rubber lifters losing integrity over time is a complete myth. In fact I prefer to use them over any alternative. There have been a few cases i have heard of, including the ones listed above and most of them involved human error. It looks like I am not yet ready to become the private investigator I want to be, but after looking at some reviews I actually might fit in. Have any of you checked out the investigator reviews on angie's list?