T  H  E      D  E  T  A  I  L

Monday, April 29, 2002

Good morning via the "Detail," a weekly e-mail newsletter that greets latent print examiners around the globe every Monday morning. The purpose of the Detail is to help keep you informed of the current state of affairs in the latent print community, to provide an avenue to circulate original fingerprint-related articles, and to announce important events as they happen in our field.

For the last two weeks, we have looked at the McKie comparison statement and petition available for latent print examiners worldwide to support.  There are only a few days left to get your name on the 'first round' list, so please act accordingly.  This week, we turn our attention to a processing technique that Dave Wade is doing a great job at spreading the word about.  

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Processing Tape with Titanium Dioxide (Tio₂)

In August of 2001, I was fortunate enough to attend the Administrative Advanced Latent Fingerprint School at the FBI Academy.  One of the requirements of this course is that you do a research project on a fingerprint related topic.  I chose “Development of Latent Prints on Adhesive Material”.  While researching the topic, I read an article that mentioned using SPR in place of Sticky-Side Powder for processing electrical tape.  The reason for this was that it was somewhat easier to see than the Sticky-Side Powder.  I mentioned this to Carl Keener, who was one of the instructors for the course.  He said that SPR is nearly as dark in color as Sticky-Side Powder.  He mentioned that he had some of Sirchie’s white SPR in the lab, but he had not had much success with it.

Sirchie’s white SPR comes in a liquid form, which contains a small amount of titanium dioxide (TiO₂), tergitol, and water.  When I tried using it on black electrical tape, it simply turned the tape gray.  I then added some Kodak Photo-Flo to the SPR.  I processed a piece of electrical tape by agitating it in the mixture to keep the TiO₂ particles in suspension.  After about a minute, I removed the tape and allowed the mixture to drain off.  Very clear white prints were visible on the tape.


Latent print developed with TiO₂ powder on the adhesive side of black electrical tape

After returning to Albuquerque, I continued experimenting with this process.  Since TiO₂ is a common pigment in paint, I contacted a local company that makes paint and explained what I was working on.  They gladly provided me with a large bag of Kerr-McGee CR-880 titanium dioxide.  I found that simply using the TiO₂ powder in place of Sticky-Side Powder produced excellent results.


Nice level three detail developed with TiO₂ powder on adhesive side of black electrical tape

Mix the powder with a 50/50 mixture of water and Kodak Photo-Flo until you have a paste.  Apply it to the tape, just as you would Sticky-Side Powder, but apply it to both sides of the tape.  Rinse the paste off the tape and the developed latents will be visible.  This process will develop latents on both sides of the tape.  Allow the tape to dry.  The developed latents will be delicate and can be easily wiped off, especially on the non-adhesive side, so be careful.  This method works especially well on the adhesive side of electrical tape and the non-adhesive side of duct tape.  If you are processing duct tape, I recommend processing the adhesive side with Sticky-Side Powder and the non-adhesive side with TiO₂ paste.  The two processes will not interfere with each other.


Latent prints developed on the NON-adhesive side of duct tape with
You can also make a solution in a tray to process larger items or pieces of tape.  Simply pour a 50/50 mixture of water and Kodak Photo-Flo into a tray and stir in TiO₂ powder until the mixture looks like milk.  Agitate the item to be processed in the mixture for approximately 2 minutes, then rinse.  Allow the item to dry, then examine for developed latents.

These processes also work well on plastic bags and cellophane.

You must use a rutile form of TiO₂, not an anatase form.  One of the best is Kemira 820.  It can be obtained from Steve Parker at Kalamazoo Paper Chemicals for about $4 a pound.  Contact him via e-mail at KalPaperChem@compuserve.com.

I have successfully used this process many times to develop workable latents on electrical tape, duct tape, and plastic bags.  Recently, one of our Field Investigators, Kevin Sanchez, brought me a shattered car window from the scene of an auto burglary.  The offender had apparently applied black duct tape to a window of a Sheriff’s Department vehicle before breaking it.  He then took the shotgun out of the vehicle, but left the broken window with the tape on it.  I left the tape as it was, still attached to the glass, and processed the non-adhesive side with a TiO₂ paste.  Numerous white prints  of AFIS quality were visible on the tape.  I immediately entered one print into AFIS, which hit on a suspect.

An article on this process will be in an issue of the Journal of Forensic Identification later this year.  If you have any questions, please contact me via e-mail at DWade@cabq.gov or visit my website at www.whiteprint.com.

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As usual, the CLPEX chat board (http://www.clpex.com/phpBB/viewforum.php?f=2) is available this week for informal banter about the Weekly Detail, as is the onin.com forum (http://onin.com/fp/wwwbd/) for other discussion.  If YOU have a processing technique that you have tested, validated, etc... and would like to share, please e-mail me.  Spreading the word about new techniques is one of the main reasons I created the Detail.

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Until next Monday morning, don't work too hard or too little.

Have a GREAT week!