Friends of the Forensic Science Club, this week we present the paper “Unlocking the potential of forensic traces: Analytical approaches to generate investigative leads”, by Varela-Morillas, A.; Suhling, K. and Frascione, N. (2022), in which authors carry out a revision of previous literature about forensic and criminalistic research methods, to explore new horizons that appear with the idea of improving methodology and technique.
The objective of forensic analysis is to gather information from the traces found at the crime scene through an objective examination. It is a process that provides supporting information for the criminal investigation, and even in many occasions, decisive information.
Currently, there are many lines of investigation that are trying to accelerate (and some are already doing so effectively) the way in which the information obtained from the analysis of biomaterials is collected and connected. It is also important to mention that the technology used for this is increasingly portable, allowing for rapid, on-site analysis of samples.
However, recent research in the field of forensic analysis has shown that this represents only a fraction of all the information that could potentially be gathered from such data.
Driven by this need, experts decided to investigate what else can be obtained from forensic biological traces and how to meet the new needs of the field by looking beyond common analytical approaches such as physical and microscopic examination.
In particular, data that can help reconstruct the chain of events, elucidate crime scene dynamics, and discover more about the actual nature of the trace and the identity of the donor, who, in this case, is the individual who left a particular trace.
The purpose of the review conducted by the experts, which can be viewed in full in the original article, is to evaluate how research has approached the acquisition of investigative information from some of the most common types of biological traces found at crime scenes: bodily fluids, finger marks, hair….
Authors specify that special attention is given to analytical techniques that can be used in scenarios where traditional analysis is not possible, where both the environment and the samples allow for non-destructivity.
They mention several types of samples, but lets’s focus on biological fluids to explore the main idea of the article.
In the initial stage of a crime scene investigation, stains of possible bodily fluids are sometimes encountered. A well-known technique for this task is the use of alternative light sources to enhance the viewing of latent stains.
Once the stain is found, its nature must be determined. The idea is to discriminate between a body fluid stain, such as blood, from a visually similar substance, such as wine; which is valuable information in suspected violent crime scenes.
In addition, there are cases where further discrimination is required, such as determining whether a bloodstain is peripheral or menstrual, which can also play a very relevant role in cases of suspected sexual assault.
Most standard methods employ reagents that, when exposed to a body fluid, produce a characteristic signal output, for example, a color change, indicating the type of body fluid present. Although useful, they can give false positives. In addition, it may be the case that a limited amount of dye is available.
Due to the limitations shown by current techniques, efforts have been devoted to the development of more robust methods to identify these types of fluids.
One study demonstrated the possibility of extracting RNA from samples that had been stored for long periods of time. This information could be of great value in criminal investigation, especially in cases of suspected sexual assault, where the true nature of the crime is still unclear.
Standard practices in the examination of biological fingerprints, strands of hair, lifted fingerprints…, over the past several decades, primarily involved visual examination of the print to identify unique physical characteristics or chemical reactions indicating a particular composition. These methods have proven to be not as reliable as one would like, as they can sometimes fall into subjectivity and unspecificity, as they can be cross-referenced with other substances.
One field that has proven valuable in solving this type of problem is forensic genetics. Through the study of DNA, it has been possible to collect much data from minute biological fingerprints.
Authors propose, throughout the original article, some novel methods that have been explored before and reflect on the need for more research in the forensic field to design methods that adjust to the changes in crime as society advances.
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