HomeLab & Science NewsArticlesHow can proper CA fuming be done at the crime scene?

How can proper CA fuming be done at the crime scene?

By Ryan M. Rezzelle, Crime Scene Supervisor for the Johnson County (KS) Sheriff's Office Criminalistics
On Friday, March 18, 2011
In Articles

Problem: Cyanoacrylate ester (CA) fuming (superglue fuming) is a preferred method of processing non-porous items of evidence for latent prints, but the proper application of CA fuming at crime scenes has historically been problematic.

Current methods offer little or no operability in the following areas: an integrated means for controlling the fuming process, regulating heat and humidity, and dealing with the major personal safety hazard of releasing CA fumes directly into the user’s breathing zone.

Solution: The CApture™ Portable Fuming System by Labconco Corporation is a new field device for cyanoacrylate fuming that is a stand-alone, portable unit that gives the user control of the hot plate temperature and humidity level in the fuming chamber. Because the unit includes a filtered fume exhaust the fuming process can be stopped quickly preventing overdevelopment while protecting the user from exposure to CA fumes. The CApture quells the frustrations of days gone by for the use of cyanoacrylate ester fuming at crime scenes.

Anybody can pick up a brush and black powder and have a positive impact on the search for latent prints at a crime scene. But one significant study (Perkins/Thomas, JFI 41 (3), 1991, 157-161) has shown that a greater percentage of latent prints are developed when appropriate evidence is processed with CA fuming prior to transport from the crime scene.

The CApture by Labconco Corporation is a practical solution that, regardless of the user’s prior forensic training, is a device that easily enables proper CA fuming techniques at the crime scene. The CApture offers a great deal of control, which is an absolute necessity for processing evidence with CA fuming.

The CApture’s microprocessor-controlled hot plate is integrated into the body of the unit with an easy-to-use LCD display. The hot plate offers temperatures ranging from 120° to 350°F(50° to 177° C) and allows for adjustments in 1° increments. The CApture works with standard fuming procedures as well as the microburst method employed by some agencies. A major advantage of this system is portability. It weighs less than 25 pounds and is equipped with a comfort grip handle for easy carrying. The carry-ready dimensions of the kit are approximately 10.5” W x 19”H x 10”D. When the clear case fuming chamber is attached to the body, upright and ready for use, the operating dimensions increase to approximately 10.5”W x 19”H x 16”D.

The bottom line, the CApture facilitates mobility and agility in approaching a crime scene. The CApture assembles and can be ready for use in less than one minute. The CApture needs only a moderately flat surface for work place compatibility while fuming. The interior measurements of the fuming chamber are approximately 10”W x 18.5”H x 8”D, which for field use is a convenient size. It comes with an integrated support rack that holds a metal-wire shelf and a rack-supported evidence hanger to free-hang evidence in the chamber. A perforated metal cover for the shelf can be employed for additional support as necessary. hookandshelf

Sufficient humidity in the chamber during fuming is the critical element of the process that fixes the developed prints. If the humidity is too low, the fumes will form a visible residue as expected, but it will be ashy in texture and will wipe away from the evidence surface, taking with it the print that may have developed.

The CApture allows for the addition of humidity to the fuming chamber in the form of two heater receptacles: one is the drop pan for the superglue and the other is a water pan. Water can be added prior to adding the glue to increase the overall humidity in the chamber. In addition, a control slide can be used so each fuming event can be monitored and quality checked before post-processed evidence is handled.

This is smart evidence handling as well as good laboratory practice, and compatible with forensic laboratory accreditation requirements (if you happen to be in that line of work).

Other portable systems use collapsible plastic enclosures that have seams from which fumes escape, or plastic bags that must be pulled over a chemical hot plate or a chemical reaction that cannot be controlled. Both options leave the user in “duck and cover” mode when the fumes are to be released. With the CApture, there is a gasket around the fuming tank to ensure that fumes stay in the fuming chamber during the fuming process. After processing, the fumes are safely purged from the chamber through the combination activated carbon/HEPA filtered exhaust. The filter has been tested for at least 100 development cycles.

Fingerprints as evidence are extremely fragile. The process of transporting evidence from the scene and entering it into a formal chain-of-custody, as well as the act of delivering it to a latent print examiner for processing, self-defines the source of the destruction: HANDLING. Once developed using CA fuming, the prints are protected to a much greater extent, but careful handling should still be employed. The CApture is not designed to take latent print examiners out of the equation. The goal is to make widely available tools and techniques that give the "good guys" a better chance for success when protecting vital evidence from a crime scene.

One thing to consider is that the CApture needs wired-power to operate. The unit can run off a 75 W inverter or an accessory field battery kit is available. Another potential low cost solution for on-demand power is a portable, rechargeable power station, which can be found at most hardware or automotive supply stores. The CApture is truly a 100% mobile device that is user friendly, easy to operate, and a great method for preserving latent print evidence at the crime scene.

The benefits of the CApture in the field are clear, but this model could very easily serve as a more permanent facility-based option (vehicle processing garage, police station, crime lab, etc.) for CA fuming in routine evidence processing. No matter how you employ a CApture, in your facility or out on the streets, it is an essential tool for on-the-go latent print processing that no agency should be without.

Ryan M. Rezzelle is the Crime Scene Supervisor for the Johnson County (KS) Sheriff's Office Criminalistics Laboratory. Ryan used his crime scene practical experience to aid Labconco Corporation during the CApture's design process. Ryan is a satisfied CApture user and may be contacted with questions at Ryan@Rezzelle@jocogov.org. Labconco's Product Manager, Kelly Williams, may be contacted with questions at KWilliams@labconco.com.

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Labconco offers a variety of forensic equipment, including Protector Evidence Drying Cabinets, Protector Downdraft Powder Stations and CApture Portable Fuming Systems.

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