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Introduction to Analytical Techniques for Forensic Analysis

Megha Walia1*, Bhoopesh Kumar Sharma1 and Faray Jamal2

1Department of Forensic Science, SGT University Gurugram, Haryana, India

2Central Forensic Science Laboratory, Bhopal, Madhya Pradesh, India

Abstract

Forensic analysis is the application of scientific techniques to investigate and solve crimes or other legal issues. Analytical techniques play a crucial role in forensic analysis as they provide valuable information that can be used as evidence in court. Globally, the forensic sciences are utilized to settle disputes of the civil court, employ criminal laws, govern the created rules fairly, and safeguard public health. Forensic Science or Criminalistics is the application of science to law enforcement. Forensic scientists rely on instrumental examination of trace quantities of substances such as pharmaceuticals, toxicological specimens, fibers, glass, GSR, and soil etc. Individualization of evidence is facilitated by variances in manufacturing chemical composition, allowing for a high degree of differentiation even with minute pieces. The purpose of this chapter is to emphasize the qualitative and quantitative analytical techniques, such as IR Spectroscopy, UV-Visible Spectroscopy, AAS, NMR, Chromatography, Microscopic techniques, EDX, XRD, and nanotechnology, employed in criminalistics for the examination of vital and soupcon evidences that are procured from various scene regions.

Keywords: Analytical techniques, instrumentation, spectroscopy, NMR, chromatography, microscopic techniques, EDX, XRD

1.1 Introduction

The evolution and development of Forensic Science is not something that has occurred in the recent past but has its root situated back to ancient Roman and Greek societies. As most of the English words are adopted and utilized in English, the term “forensic” is no exception and thus has its roots to the Latin language, wherein it refers to ‘of the forum’ where in ancient time law courts with discussion were held [1]. An area of study known as “forensic science” is one in which scientific principles are utilized in the course of a criminal investigation for the purpose of conducting an evaluation of the evidence that has been gathered over the course of the inquiry [2]. Forensic sciences use several disciplines, including the basic sciences-physics, chemistry, mathematics, and biology, along with law (both civil and criminal), engineering, dentistry, geology, microbiology, biotechnology to name a few and incorporate them to analyze the physical evidence [1]. In other words, forensic science applies scientific knowledge to the definition and execution of the law [3]. In fact, Forensic Discipline is acknowledged in and of itself as a science that draws from a variety of other fields. The amalgamation of all the sciences with the sole responsibility to assist the criminal justice system is the appropriate definition of Forensic Science. Forensic science is a realm that has indefinite possibilities [1].

The team that consists of people participating in the examination and investigation of crime scenes incorporate medics, police, and forensic professionals who are accountable for the collection of evidence. Laboratory-based forensic scientists/experts are more familiar with the many analytical procedures utilized for their analysis [2].

As a three-part structure, Forensic Science consists of

• Collection: Associated with Inquiry of Facts (Science);
• Examination: Associated with Generation of Results;
• Presentation: Associated with the Court of Law [3]

1.1.1 Forensic Analysis

Analysis of any crime scene requires the person to be competent in the domain of physical and biological sciences, including other sectors of technology and law enforcement. Forensic experts examine and analyze fingerprint ridges, fabrics, glass, and residues from gunshot, assess medications and poisons, investigate possibilities of forgeries, and inspect residues for any possible incendiary and explosive crimes [4]. Human body fluids such as blood, urine, seminal fluid, and saliva play a major role in the investigation of crimes like murder and rape [5]. Since forensics is primarily a scientific discipline, an extensive array of analytical methods is employed to examine evidence collected at the site of the crime. There is a plethora of information stored in this evidence; it just needs the right eye for identification. This motivation has fueled the development of forensic science, where information is gained via the analysis of numerous types of evidence to help the legal system in piecing together the past [2].

According to forensic community-recognized criteria, the result that is generated after thorough examination should be statistically correct and should always have high probability in reaching a fair and just decision. No categorical judgements are permitted unless the samples being compared have entirely distinct physicochemical profiles that are regarded as having a confidence level of one hundred percent [6–8].

Therefore, interpreting data as categorical while ignoring the “fuzziness of limits” may result in forensic malpractice.

Most known to occur during an investigation are biological, physical, and chemical evidence. Typically, these samples are prepared prior to examination utilizing analytical procedures to guarantee optimal analysis [2].

Application of analytical chemistry in forensic is one of the most helpful and initiating fields of research, with widespread usage in areas such as the examination of illicit and illegal narcotics in diverse matrices, the analysis of food adulteration, the analysis of adulteration of fuels and car chassis, and the analysis of frauds in works of arson [1].

They are two types of forensic analytical methods:

1. Destructive methods: This entails the destruction of the evidence and the loss of evidence integrity. Chromatographic procedures are examples.
2. Non-Destructive methods: This procedure preserves the integrity of the evidence because it does not entail the destruction of the evidence. Examples include microscopy and spectroscopy [9].

1.1.2 Introduction to Instrumentation in Forensic Science

In criminal and civil investigations, forensic science involves the use of sophisticated scientific methods. This right eye with the correct instrumental technique can not only just recognize, but detect and even segregate the articles found at the crime scene to forensically relevant material.

Figure 1.1 Types of evidence analyzed with various instrumental analysis.

This relevant material has stored incriminating stories regarding the event, the identity of the origin (who, what, with) and of the incident (how, when, why, where) that generated it [10]. The likelihood ratio method was given special study by Biosa et al., who provided clarity on the interpretation of analytical data in the forensic context. The data has been classified into two categories using penalized logistic regression and the computation of likelihood ratios. Using data on alcohol biomarkers, the approach was utilized to categorize individuals who often consume alcoholic beverages [11]. Figure 1.1 depicts the physical, chemical, and biological evidence that can be analyzed by various instrumental techniques.

The numerous approaches to evidence analysis are going to be broken down into their essential components and outlined in this chapter [6–8].

1.1.2.1 Validation of Instrument

As never before, the legitimacy and credibility of forensic expert testimony, as well as its capacity to distinguish between defense and prosecution positions, are being challenged as well as questioned [12, 13].

Therefore, it is inevitable that the scientific basis of forensics would be questioned; thus, it is essential to shift the attention to the integrity of the investigation procedure. Thus prior to the deployment of any new forensic procedure, certain efforts must be performed to confirm the efficiency of the suggested method for its planned use i.e., every new procedure must be verified/validated. Analytical procedures have evolved greatly with time, from extremely subjective evaluations of data with limited information to objective evaluation using chromatographic and spectroscopic signals with detailed information [8]. To completely comprehend the efficiency of an instrument, experts must be conversant with the general features of investigative assays. This includes the limit of detection (LOD), the signal-to-noise ratio (S/N), the limit of quantification (LOQ), accuracy, precision, interference, and resilience. Due to the significance of such factors for defining evaluates, they are crucial mechanisms of validation of method. Numerous investigative equipment alter a specific characteristic of an analyte into an electrical indicator. Numerous factors, including arbitrary electrical transmissions, varying chemical concentrations innate to the sensor, which leads to undesired signals which might hinder the response of the target. Such irregular impulses are referred to as noise. The finest machinery enhances S/N by enhancing analyte signal, reducing noise, or both. A high S/N ratio reduces LOQ and LOD. These limits are often derived by gauging successive dilutions of an evidence in the matrix of interest and...