Application of Amido Black Mixture for the Development of Blood-based Fingerprints on Human Skin

Transcription

1 Case Report Application of Amido Black Mixture for the Development of Blood-based Fingerprints on Human Skin Rodney Lawley Birmingham Police Department Birmingham, AL Abstract: Amido black is a chemical blood reagent often used by forensic specialists in the development of blood-based latent prints on porous and nonporous surfaces. The effectiveness of this chemical was recently tested on the dermal surface of a homicide victim. The results were impressive, and further forensic study in this area appears to be warranted. Introduction Forensic specialists are familiar with the chemical amido black. It is a suggested treatment of visible prints and latent prints that have been deposited in blood [1]. Amido black is primarily composed of the substance napthol blue black. The remaining ingredients will depend on the type of mixture that is being prepared [1], but in this case, the methanol-based mixture (2 g napthol blue black, 100 ml glacial acetic acid, and 900 ml methanol) was used. Amido black is a chemical dye solution that binds to protein molecules in blood and yields a dark blue color [2]. This color change darkens the bloody area to such a degree that many fine details, such as dermal ridge impressions, can become clearly visible. 404 / 53 (4), 2003

2 As one might imagine, a chemical such as amido black is highly useful at any crime scene involving the possibility of evidentiary impressions in blood. Common crime scene applications include the development of bloody footwear impressions on flooring, fabric impressions from bloodstained clothing, and friction ridge impressions on a multitude of porous and nonporous surface types. With the exceptional versatility of this mixture in mind, forensic investigators in Birmingham, Alabama recently considered the use of amido black as a potential latent-developing agent for bloody stains on the skin of a homicide victim. Although there were some concerns that dermal saturation and skin tone would reduce the necessary contrast in the amido dye, the investigators decided that an attempt at this procedure was warranted. Procedure The victim s body, with multiple stab wounds to the upper torso, was discovered on the interior floor of her home. Bloody smears were observed on the ankles, both legs, and the wrist area of both hands. This evidence strongly indicated the possibility of a violent physical struggle between the victim and the attacker. Because of these initial observations, investigators explored the possibility of developing latent blood prints on the dermal surface of the applicable body parts. This possibility, along with a thorough latent search of the victim s residence, became an early focus of the crime scene investigation. The body was first examined with an alternate light source (ALS) for serological fluids, inherently fluorescent latent prints, and other types of trace evidence that would be beneficial to the investigation. This procedure produced no ridge detail but did indicate the possibility of finger marks on the inner thigh of the victim. A decision was made to remove the body (prior to any further latent search) to the county coroner s office for the collection of any available serological evidence. This transfer was necessary because of the fragile nature of potential DNA evidence and the biologically destructive properties that are often inherent to many chemical-based latent search procedures. Great care was taken during the removal of the body from the crime scene. 53 (4), 2003 \ 405

3 Investigators were well aware that any dermal contact could destroy a potential case-solving latent print. Upon conclusion of the coroner s examination, the body was fumed with cyanoacrylate acetate (super glue) utilizing an oversized body bag as a makeshift fuming chamber on the autopsy table. Although some sources [1] indicate that cyanoacrylate fuming is detrimental to the amido black processing procedure, other sources [3] report that preprocessing with cyanoacrylate fumes is not deleterious to amido black on most substrates. This, coupled with established latent-search methods that included the fuming technique, suggested fuming and then subsequent amido black treatments as a practicable processing sequence. Following this short fuming procedure, investigators conducted an immediate examination of the dermal surface utilizing the ALS. No latent prints appeared. Investigators then used a feather-type fingerprint brush to apply a fluorescent powder to the skin surface. The results of this process were also negative. At this point in the investigation, a decision was made to apply amido black to the bloodstained areas of the body. The developer was lightly sprayed onto the affected area using a common spray bottle. The mixture was sprayed just above the target area, allowing the dye to slowly gravitate across the surface of the bloodstain. This indirect application of the mist prevents the impact damage that could occur if the fluid were to be sprayed directly upon the stain. Because of concerns about unwanted dermal saturation and poor contrast of the amido dye with the dark complexion of the body, amido exposure was limited to approximately thirty seconds. This immersion application was immediately followed with a rinse solution (10% glacial acetic acid and 90% methanol) as recommended by the Processing Guide. Again, the rinse solution was also sprayed above the target area and allowed to slowly gravitate across the stain. 406 / 53 (4), 2003

4 Results Utilizing the described amido black immersion, previously undetected ridge detail was located on the inner right thigh of the body. This detail, though not sufficient for a suspect comparison, demonstrated the promise this new application could hold for future homicide investigations. An additional nonridge imprint of the attacker s finger position was obtained on the same upper thigh area of the deceased. Although this evidence is of little value for the identification of a suspect, it could prove to be a crucial element of evidence when coupled with witness testimony, the statement of a potential suspect, or other corroborating evidence. Discussion This attempt at developing blood-based prints on human tissue was a success. Still, there are many factors that could preclude the duplication of this success in similar investigations. It should be noted that the victim in this particular case was deceased for at least twenty-four hours prior to any attempts at developing latent images on the skin. Additionally, the body had been stored overnight in a refrigerated storage chamber (between 37 and 40 EF) and was then stored at room temperature for approximately two hours prior to processing. These factors alone can greatly influence the plasticity and absorption ability of the dermal tissue. Both of these characteristics can influence the success rate of any latent search conducted on human skin. Skin tone should also be considered as a pertinent factor when planning a latent search of this nature. The dark blue color of the amido black dye will not contrast well on skin that is of a similar dark color. Although other blood reagent dyes were not tested in this case, it is logical that similar results could be obtained with available blood reagents of many different colors. Conclusion Amido black is a viable forensic tool in the enhancement of blood prints on human skin tissue. It is versatile, inexpensive, 53 (4), 2003 \ 407

5 easily obtainable, and portable enough to take into the field for field investigations. Continued cautious experimentation with amido black, as well as other latent-developing chemicals, should result in further improvements in this growing subfield involving the latent print processing of dermal tissue. More than ever, forensic investigators must be aware of the various chemical tools that are available for their use in any latent print search. Additionally, they must have the confidence to apply these tools when applicable circumstances are present. For further information, please contact: Sergeant Rodney Lawley Forensic Unit Supervisor Birmingham Police Department st Avenue N. Birmingham, AL (205) References 1. Chemical Formulas and Processing Guide for Developing Latent Prints; Federal Bureau of Investigation, US Department of Justice, US Government Printing Office: Washington, DC, Warrick, P. Identification of Blood Prints on Fabric Using Amido Black and Digital Enhancement. J. For. Ident. 2000, 50 (1), McCarthy, M. M.; Grieve, D. L. Preprocessing with Cyanoacrylate Ester Fuming for Fingerprint Impressions in Blood. J. For. Ident. 1989, 39 (1), / 53 (4), 2003