Exploring the recovery and detection of messenger RNA and DNA from enhanced fingermarks in blood

Recent Advances in Enhancement Techniques for Blood Fingerprints

The blood fingerprint enhancement is not so eye-catching as latent fingerprint development in forensic community, but it is indeed an important piece of evidence for personal identification, forensic analysis and even reconstruction of crime scenes. In over past ten years, novel reagents, advanced materials and emerging techniques have growingly participated in blood fingerprint enhancement, which not only leads to a higher level of developing sensitivity, selectivity and contrast, but also endows blood impressions with more forensic significance. This review summarizes recent advances in conventional chemical reagents targeting at heme, protein and amino acid as well as emerging enhancement techniques based on advanced materials, new equipment or methods. Some critical issues in forensic science are also discussed, including partial blood fingerprint enhancement, false positive of developing reagents, the compatibility of blood enhancement technique and DNA, fingerprint age determination, and so on. Finally, we have proposed several urgent problems to be solved and the prospects of some promising techniques were proposed in the field of blood fingerprint enhancement in future work.

On the Identification of Body Fluids and Tissues: A Crucial Link in the Investigation and Solution of Crime

Body fluid and body tissue identification are important in forensic science as they can provide key evidence in a criminal investigation and may assist the court in reaching conclusions. Establishing a link between identifying the fluid or tissue and the DNA profile adds further weight to this evidence. Many forensic laboratories retain techniques for the identification of biological fluids that have been widely used for some time. More recently, many different biomarkers and technologies have been proposed for identification of body fluids and tissues of forensic relevance some of which are now used in forensic casework. Here, we summarize the role of body fluid/ tissue identification in the evaluation of forensic evidence, describe how such evidence is detected at the crime scene and in the laboratory, elaborate different technologies available to do this, and reflect real life experiences. We explain how, by including this information, crucial links can be made to aid in the investigation and solution of crime.

Back to Amido Black: Uncovering touch DNA in blood-contaminated fingermarks

Blood-contaminated fingermarks (FMs) found in violent crime scenes may directly connect the suspect to the crime by linking the FM to the suspect and the DNA from the blood to the victim. However, marks that are incomparable are considered "dead-evidence" as the link to the suspect is lost. In this study, a novel approach was attempted to uncover the trace amount of touch DNA of the suspect in such marks. We examined the effect of two enhancement methods, ninhydrin (NIN) and amido black (AB), on DNA recovery from blood-contaminated FMs. A total of 108 fingerprints were deposited in three sets of depleted blood prints, blood-contaminated FMs, and latent FMs. All FMs were developed by either NIN or AB, or left undeveloped as reference followed by the quantification of the total DNA amount. This work shows that while AB had a detrimental effect on the quantity of blood-derived DNA specifically, reducing it by half, no similar effect was observed for touch DNA in latent FMs. This reduction led to the alteration of the major-to-minor DNA profile ratio to 70:30, thus enabling to obtain two distinct DNA profiles of the suspect from the touch DNA as well as the victim's profile from the blood. From an operational perspective, the use of AB in crime scenes may have an added value to retrieve the crucial DNA profile of the suspect, thus resurrecting a "dead-evidence."

Practical evaluation of an RNA-based saliva identification method

Identifying saliva in samples found at crime scenes is important to clarify the tissue origin of DNA obtained for identification of individuals. Recently, a novel messenger RNA-based approach using two saliva-specific markers, Statherin (STATH) and Histatin 3 (HTN3), has been reported. This method can identify saliva more specifically than conventional amylase-based methods. Here, we performed several evaluations related to applying this method to real-world forensic work. First, we evaluated the effects of exposure to blue light (450nm) or to the reagent on Phadebas paper, which are direct methods used to locate saliva stains, on the stability of the RNA markers. The results demonstrate that exposure to the two direct tests did not affect the stability of the RNA markers. Second, we performed a comparative analysis of RNA-based and amylase-based conventional methods to examine the sensitivity and stability of the markers under various storage conditions. Although there was no difference in the sensitivity of the two methods for detecting 1-day-old saliva stains, a time-course study demonstrated that the RNA saliva markers were less stable than amylase, especially in wet conditions. During this time-course experiment, the stability of human DNA was also investigated. Although DNA was also unstable in wet conditions, it was more stable than the RNA markers in dry conditions. Taking the above results into consideration, we suggest that the RNA method could be introduced to current saliva identification procedures and should be used as a supplementary method to strongly support identification of saliva by the amylase-based method.

The effect of mark enhancement techniques on the subsequent detection of semen/spermatozoa

Fingermarks, footwear marks, blood and semen are amongst the most commonly encountered types of evidence at crime scenes. Previous work has extensively investigated fingermark and blood enhancement techniques and a sequence developed to maximise evidence recovery; however, there is limited research as to the effect of these techniques on the subsequent detection of body fluids such as semen. In this study, seven fingermark and blood enhancement techniques (e.g. powder suspension, cyanoacrylate fuming and acid violet 17) were employed followed by the subsequent detection of semen/spermatozoa. Other variables included in the study were the use of two substrates (white ceramic tiles and grey laminate flooring), a depletion series and ageing periods of 1, 7, 14 and 28 days. The effect these techniques had on the subsequent detection of semen was assessed by visual and fluorescence examination followed by presumptive and confirmatory testing for semen and spermatozoa. The results found that protein stains (acid violet 17 and acid yellow 7) caused a loss in presumptive test reactivity; however, sperm heads were still observed using microscopic examination after extraction and staining. The use of black magnetic powder, Bluestar(®) Forensic Magnum luminol, Lumicyano™ 4% and cyanoacrylate fuming followed by basic yellow 40 staining did not hinder subsequent presumptive and confirmatory tests for semen and sperm heads. Powder suspension caused a loss in both presumptive test reactivity and sperm heads from the substrate. In general, the enhancement techniques resulted in the improved visualisation of the semen stains under white and violet/blue light. The results from this study aim to provide a strategy to maximise evidence recovery and improve efficiency in an integrated forensic approach.