CLPEX Chat Board

I had a question from an officer on our dive team. He wanted to know what our procedures are regarding water soaked guns that need processing for latent print development.

I located an article on SPR in the Journal of Forensic Sciences entitled “Small Particle Reagent: Developing Latent Prints on Water-Soaked Firearms and Effect on Firearms Analysis”. The article describes the SPR method used to develop latent impressions on guns immersed in water and the affect on the firearms’ functionality. The article indicates that developing latent impressions on water-soaked firearms with SPR produced better results than CAE fuming alone followed by black fingerprint powder.

The article was published in March of 1988. I could find no subsequent articles using other development techniques with SPR. Typically our lab processes guns with CAE and a florescent dye stain. That method was not tested against SPR in this article, so I am uncertain how SPR performs in relation to the method we currently use. The article does state that CAE can be used after applying SPR.

Could someone advise what methods or sequential methods other labs use to process wet nonporous items? Has anyone tried using CAE and dye staining after SPR?

Our laboratory also uses the CAE/dye stain method for latent print development on firearms. One problem that arises is that once you take the firearm out of the water it begins to rust, sometimes quite quickly. We advise our crime scene teams and our service agencies that the firearm should try and be recovered and kept in water, preferably the water it was found in, and transported to the laboratory. This way the firearm will be removed from the water, allowed to air dry and processed conventionally as quickly as possible.

I personally have not had much success with SPR. I've tried it before earlier in my career, but never had consistent results.

I have found SPR immensly useful when I know the brass is coming through the lab or VIPS are taking a tour. I have a white ceramic coffee mug that I clean really well, then put a good oily set of fingerprints on. I leave the mug by the sink, with the squirt bottle of SPR off to the side. Then, when someone on the tour asks "What's new?" I offer a demonstration. I turn on the cold water and hold the mug under it while explaining that in the old days, anything washed off with water was useless for fingerprints. But now with modern technology, we can work miracles. Then I move the mug from under the running water and spray it down, then rinse it off. Beautiful fingerprints! It amazes them. Yeah, we're really on the cutting edge here. Something they never saw on CSI. Great stuff, SPR.

Thomas,

I know I'm getting a little off topic, but how much do you actually use SPR in casework and how consistent are your results? Just curious.

I agree that its a cool technique to use for demonstration. My personal favorite is the flame method using twisted up masking tape....also very cool.

Hi Patrick,
Actually, I did use SPR once at a crime scene. There was a recovered stolen car and it had just started to rain, maybe a half hour before I got the call. Seemed like the perfect opportunity. Sprayed that sucker down in the rain and let the rain wash it off. Unfortunately, I don't remember if it developed any latent prints or not. To the best of my memory, that's the only time I can remember actually using the stuff for anything except to show off for the boss.

A specific case I can recall was a recovered stolen vehicle. It rained on the vehicle while I was on my way to the scene, although the rain stopped about the time that I arrived. The owner had been notified and was waiting to reclaim his vehicle; the requesting agency did not want to delay the processing of the outside of the vehicle to allow it to dry.

I used SPR, developed latent prints, & later was able to make an ID.

Similar situations with wet vehicles & limited access times for processing, along with drug labs with contaminated evidence (i.e., glassware) comprised the primary uses of SPR. Have had a fair amount of success in those situations. Certainly more than the alternative would have been - no other viable processing method available at the time = zero latent prints.
Regards, RLT