CLPEX Chat Board

So, I've looked around a bit on this board and did some searching, but I didn't find the answer I was looking for so I'll ask it here.

When processing tape, both sticky side and non-sticky side, what is the best method for doing that? Currently, we are taking the lengths of tape, affixing the ends to a peice of acetate paper (transparency paper) so the sticky side is (mostly) adhering on the ends, placing that in to our fuming chamber so the non-sticky side is getting fumed. Once fumed, we remove the tape from the acetate paper, process the sticky side with wetwop or lightning liquinox, then dye stain the non-sticky side. I guess I'm a little concerned that I may be destroying any potential latents on the ends of the tape as that is where the majority of the latents would be recovered (you touch the ends of the tape when you tear it off the roll or place it on a surface). Is this the correct way or is there a better way to do it? Any help would be appreciated.

I process tape pretty much the way you've described your methods, however, I usually process the non-adhesive side first with a dye stain, swab the non-adhesive side, and then process the adhesive side with Wet-Wop. FWIW in my experience, it certainly seems like duct tape needs to be left in the CA chamber a little longer than what seem people may be used to in order to get good development.

Sometimes the dye stain brings out some faint prints on the sticky side (especially on black electrical tape).

josher89 wrote:Currently, we are taking the lengths of tape, affixing the ends to a peice of acetate paper (transparency paper) so the sticky side is (mostly) adhering on the ends, placing that in to our fuming chamber so the non-sticky side is getting fumed. . . . I guess I'm a little concerned that I may be destroying any potential latents on the ends of the tape as that is where the majority of the latents would be recovered.

It has generally been my experience that the vast majority of latent prints I recover from tape are on the adhesive ends of the tape, not in the middle of the adhesive side nor anywhere on the non-adhesive side. I cringed when you state that you put the adhesive ends of the tape on acetate prior to any processing because intuitively I would expect that to disturb any latents that may be there. Have you run any experiments on a number of tape strips with your own prints testing whether placing the tape on acetate, then removing the acetate and processing with Wetwop alters the prints, as opposed to control prints on tape that was not placed on acetate?

josher89 wrote:I guess I'm a little concerned that I may be destroying any potential latents on the ends of the tape as that is where the majority of the latents would be recovered...

I, too, cringe when I am doing this but how else do I secure the tape to the acetate paper? I can smash (sic) the middle of the tape strand to the paper but then the top end will flop down. I've been doing some minimal research on the thing you mention, Pat, and am also going to be working with an ATF agent on tape from cardboard. I may decide to do a full-blown experiment but for now, I'm still having good success with duct tape but minimal with packing tape. I've only been using one kind of packing tape and I don't think the adhesive is very thick so I'm not getting great results with Lightning Liquinox. Duct tape is sooooo sticky that I'm getting good results this way. I may try to control more of the pressure placed on the ends of the tape and see if that has any effect on latent development. I was just hoping to see if there was a better way to do it.

What about just draping it over a wire rack, sticky side up?

I'm just amazed that you've got tape that isn't balled and squished together, where or how to hang it is several worries down the road.

At my agency, we actually adhere the entire length of tape to acetate before CA processing. From what we've seen, CA fuming the adhesive side of the tape has a much more deleterious effect on Wet Wop prints than adhering it to the acetate and then pulling it off. The CA fuming seems to coat over the adhesive, including the prints, and inhibits the Wet Wop staining. The acetate protects the adhesive side prints and most all tape types pull back off of the acetate quite easily and do not disturb the adhesive.

Our process then, is to remove the tape from the evidence (we use undu to aid in the removal of tape from paper or cardboard) and ahere it to the acetate. We then fume the non adhesive side. We then will then Wet Wop the tape, followed by RAM. RAM is almost always used last as it has a tendency to melt/harm the adhesive.

I did trials for “Wetwop” (BTW, the name was chosen as a ‘spin-off’ of Lightning Powder’s “Redwop” which is “powder” spelled backwards) after Kjell Carlsson, the developer of “Wetwop”, contracted for the release to the United States market through Lightning Powder Company. Kjell had developed an outstanding product for the development of latent prints on the adhesive side of tape, but Lightning Powder wanted trials on its effectiveness. These trials involved latent prints placed on the adhesive side of tape; duct, masking and cellophane. It has been some time since these trials were conducted, but I recall the contaminated tapes were placed, adhesive side down, on clear acetate sheets and left for set periods of time before being processed with “Wetwop”, crystal violet and ‘sticky side powder’ for comparative results using a split latent technique.

The tapes were not plastered down, just slightly pressed down on the sheets because you would expect that tape on evidence would be adhering to a surface. The acetate sheets permitted easy removal for processing purposes. Successful development did occur with all processes and this should be expected as the latent residue reaction is on matter being retained and held in place by the adhesive substances. It is not going anywhere. In actual cases; extreme pressure, difficult tape removal or presence of other surface contaminant(s) can adversely influence results. However, if tape has been carefully removed and lightly placed on acetate, glass or a smooth material, the adhesive side can be ‘protected’ from the effects of cyanoacrylate fumes, which SMHanna noted, do coat the surface (ever clean your fish tank!!) which can occur when processing the non-adhesive side with CA. The adhesive side can later be processed with a powder suspension solution. SMHanna’s approach is very sound except I never trusted ‘undu’ as it dissolves the adhesive and that is what is retaining the latent residue. I have heard that judicious application of ‘undu’ is fine, but I worried about using it.

BTW, when placing your tape down on a surface using tweezers or needle forceps to minimize that touching at the end of the tape concern, be sure your receiving surface is sterile. You do not want to be lifting any latent residue from that surface and compromise your evidence with added latents or DNA.

Hi Guys
In Auckland down-under, we pin the tape sticky side out onto Polystyrene sheets, the pins leave only a small hole the position of which you can carefully choose. This method has been used for around 20 yrs + and seems the best. We found that placing the sticky side to the acetate tended to flatten out the ridges during transportation lessening the chance of getting identifiable prints developed. As others have found, I also believe prints on the sticky side at the ends are the best source for offender's prints though I have found plenty part way along the tape. My own opinion is that the sticky side is protected from innocent fingers (i.e. cops at the scene).

Quite recently I had excellent prints on the sticky side of electrical tape at a scene, I luckily got good photos of one of them, unfortunately having no polystyrene on hand I stuck it to acetate sheets but by the time I got back to the office I could not see the prints. Perhaps it was the build up of heat in the car while I was attending other jobs that caused the adhesive to 'melt'; I am not sure, all I know is that the prints were no longer there.

We also cut the tape into manageable lengths.

Thanks for all of the replies. It sounds like I'm not too far off from what you all are doing. I may try pinning the tape to foam board and see how well that works but regardless, it seems that protecting the adhesive side from superglue fuming is necessary to preserve any latent detail.

Thanks again!!!

I've used either clear acetate sheets or cut open a zip top plastic evidence bag and placed the adhesive side down inside the bag (a surface that should not have been previously handled by others). I've had great results with this method for preserving the adhesive side while processing the non-adhesive side. Then, when I'm done processing the tape, all I have to do is re-seal the zip top bag and I can package the tape in paper or another plastic bag without having to worry about the tape sticking to itself or the outer package.

Josher - have you tried Crystal Violet for the clear packing tape? I've had decent luck with it over dystains or any of the sticky-side powders for clear plastic tapes.

josher89 - you may want to double check with Neville on what he's referring to as far as polystyrene. My guess is that it's a type of plastic sheet as opposed to a form of Styrofoam (extruded polystyrene).

akstephen,

Do you use CV after fuming the non-sticky side or before but just on the sticky side?

As a side note, I processed some black electrical tape on Friday. I cut a length off of the submitted roll for testing. We didn't have titamium dioxide so I thought I'd use our Lightning Liquinox recipie and sub in white powder for the black. THIS DID NOT WORK!!! Good thing it was on a test piece. I then looked up materials from a class I took a while back and they said that R6G in water was an option. Since R6G is a dye stain, I adhered another test piece to acetate, fumed for 15 min, and processed both sides. I got great results on the sticky side on untreated prints...nice and orange with a 515nm light. Not so great on the non-adhesive side.

All in all, I see a research project for some interns here. I'd like to try the CV for clear tape...let me know how you do it, akstephen, and I'll try it out!

Thanks again for all of the help!

Hi Dianne
you are correct the stuff used for dingy floatation, home insulation and as computer packaging.

Hi Josher89
I think you maybe also correct a lot has been done I guess the problem has been the number of tape out there, also in NZ we have an added issue of Parrallel imports. We are not in a protected market here so if I say duct tape I am not talking about a few products, the local $2 shop will be importing straight from china etc.