9.6: Legal Aspects of Forensic Evidence
Forensic science is simply defined as the application of science to the law or legal matters. In today’s CSI and Forensic Files world, this area of science is much more widely known to the general public. However, it is also misunderstood due to Hollywood’s resolve to complete every case within the context of a one-hour, commercials included, pseudo-real-life crime drama. When the actual real-life judicial system needs science to resolve a question, the person who is called upon to bring science into the courtroom is often a forensic scientist. The law and science are strange bedfellows. Science is an empirical method of learning, anchored to the principles of observation and discovery as to how the natural world works. Scientific knowledge increases human understanding by developing experiments that provide the scientist with an objective answer to the question presented. Through the scientific method of study, a scientist systematically observes physical evidence and methodically records the data that support or not support the scientific process. The law, on the other hand, starts out with at least two competing parties with markedly different views who use the courthouse as a battleground to argue factual issues within the context of constitutional, statutory, and decisional law.
Forensics involves the application of knowledge and technology from different scientific disciplines in jurisprudence. These are, for example, biology, pharmacy, chemistry, medicine, etc., and each of them applies in the present, increasingly complex legal proceedings in which the required knowledge and skills of experts from these areas to prove offenses. For the purposes of this article, we will hold on the biology or forensic biology, which is the most important branch of DNA analysis. Forensic biology deals with serological and DNA analysis of physiological fluids in the human body in order to identify and individuate people, animals, and microorganisms. It should be added that the application of certain procedures dates back to the earliest history of medicine, but it is still used today. These are, for example, methods in which the examination of the body (depending on its conditions) can determine gender, race, age of the person, analysis of the tooth, or the determination of blood group testing, and the presence of specific antibodies in the body.
The development of medicine throughout history has formed the special branches that now make up modern medicine. With them were created and profiles of experts whose work made a significant contribution to medical practice, but also in medicine as a scientific discipline. Thanks to their academic and professional achievements, medicine today can provide answers to questions that were once unimaginable.
DNA analysis indicates a molecule containing nucleotides with the elements that determine the development and functioning of all living beings. DNA analysis is used to cause the blood, hair follicles, saliva, or semen linked to the suspects to commit crimes.
In the criminal sense, DNA analysis confirms the fundamental principle of modern criminology, and that is “no perfect crime”. This sends a clear message to perpetrators and potential perpetrators that any criminal offense will be revealed and the perpetrator will be punished.
To learn more about how forensic evidence is analyzed, watch this video: analyzing forensic evidence .
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Criminal Investigation
Criminal investigation deals with the offense as a real phenomenon, and in the investigation, they included actions that should clarify all issues related to the appearance of the offense, the offender, the victim, and other circumstances. The criminal investigation includes microanalysis of criminal offense because it directly reconstructed the actual structure of the offense. Criminal Investigation is microanalysis, the reconstruction of the past - a possible criminal offense. The research directly reconstruction the real, objective, and subjective structure of the offense.
The application of science to the legal arena is fundamentally one of reconstruction, that is, trying to assist in determining what happened, where it happened when it happened, and who was involved. It is not concerned with, and cannot determine, why something happened (the motivation). When science is applied in this way, the adjective “forensic” is added, which means that it is applicable to a court of law. Forensic analysis is performed on evidence to assist the court in establishing physical facts so that criminal or civil disputes can be resolved. The legal question determines the direction of scientific inquiry. It is the job of the forensic scientist to translate the legal inquiry into an appropriate scientific question and to advise the judiciary on the capabilities and limitations of current techniques.
In forensic science, the laws of natural science are considered in making a determination about the state of a piece of physical evidence at the time of collection. Using the scientific method, inferences are made about how the evidence came to be in that state. These inferences then limit the events that may or may not have taken place in connection with said evidence. The law defines elements of a crime; science contributes information to assist in determining whether an element is present or absent.
The first few minutes of a crime scene’s processing can be the most critical moments of an entire investigation. At no other period will the investigators be closer to the moment the crime was committed. Investigators will never have the area more pristine or more unfettered from contamination. In those first few minutes, fingerprints, shoe prints, tire prints, trace evidence, and the state of the victim are all at their most informative. And yet, at no other time are mistakes more likely made that can potentially jeopardize the successful prosecution of the crime’s perpetrator.
Once the area is secure, investigators can then perform an initial walk-through in which they try to glean an understanding of the nature and scope of the crime and determine what evidence should be collected and from where. Prior to removing any evidence, however, it should be photographed or videotaped to document its state and its position within its surroundings. Much of the crime scene can also be recorded by 3D laser scanning to give investigators an even more refined image of the crime scene and its overall layout.
To fully appreciate the potential value of physical evidence, the investigator must understand the difference between class and individual characteristics. Characteristics of physical evidence that are common to a group of objects or persons are termed class characteristics. Regardless of how thoroughly examined, such evidence can be placed only into a broad category; an individual identification cannot be made because there is a possibility of more than one source for the evidence. Examples of this type of evidence include all unworn Nike athletic shoes of a particular model, the new, unmarked face of a manufacturer’s specific type of hammer, and soil. In contrast, evidence with individual characteristics can be identified, with a high degree of probability, as originating with a particular person or source. The ability to establish individuality distinguishes this type of physical evidence from that possessing only class characteristics. Some examples of evidence with individual characteristics are fingerprints, palm prints, and footprints.
Conceptually, the distinction between class and individual characteristics is clear. But as a practical matter, the crime scene technician or investigator often may not be able to make this differentiation and must rely on the results yielded by crime laboratory examination. Thus, although the investigator must recognize that physical evidence that allows for individualization is of more value, he or she should not dismiss evidence that appears to offer only class characteristics, because it may show individual characteristics through laboratory examination. Furthermore, a preponderance of class-characteristic evidence tying a suspect (or other items in the suspect’s possession) to the scene strengthens the case for prosecution. Note also that occasionally class-characteristic evidence may be of such an unusual nature that it has much greater value than that ordinarily associated with evidence of this type. In an Alaska case, a suspect was apprehended in the general area where a burglary had been committed; the pry bar found in his possession contained white stucco, which was of considerable importance since the building burglarized was the only white stucco building in that town. Finally, class-characteristic evidence can be useful in excluding suspects in a crime, resulting in a more effective use of investigative effort.
DNA Analysis
All cells, other than mature red blood cells, contain a nucleus that is where the body’s DNA is located. The DNA molecule is a double helix, each strand being composed of four bases, or nucleotides: cytosine, guanine, thymine, and adenine. They are usually referred to by the first letter of their name: C, G, T, and A. The two strands are held together by chemical bonding in which T always pairs with A and G always pairs with C. A gene is a part of the DNA strand in which the order of C, G, T, and A is ultimately responsible for defining which amino acids are assembled in the synthesis of a specific protein. All of the DNA in a cell is known as the genome, and there are approximately 3 billion base pairs in the human genome. This description applies only to nuclear DNA.
The history and role of deoxyribonucleic acid (DNA) as the material that carries the genetic blueprint of all biological organisms have been known since Crick and Watson’s research that was published in 1953. However, the basis of its use in forensic science is much more recent, beginning just 5 years before the Pitchfork case. Subsequent research showed that genes occupied only a very small part of the total material in a DNA molecule, and in 1980 Dr. Ray White and colleagues at the University of Utah found that some parts of the noncoding DNA were highly variable between individuals. White, a geneticist, suggested that these regions could be used in parentage testing. Dr. Jeffreys went further and showed how the variability could be used to type blood and body fluids in criminal cases.
DNA analysis is used in forensics for linking suspects to samples of blood, hair, saliva, or semen. It is used to prove guilt or innocence, and in a variety of cases that require the identification of human remains, determine maternity and paternity, establish matching organ donors and recipients, etc.
Blood patterns can be very helpful in the investigation of homicides. Passive drops, transfer/contact patterns, swipe patterns, wipe patterns, and void patterns are examples of characteristic patterns to note. Passive drops, also known as 90-degree blood drops, indicate the blood source was at a 90-degree angle from the surface of the body. Ninety-degree blood drops are not likely to be the decedent’s blood and should be collected. Transfer/contact patterns are also important blood patterns. These patterns appear when a bloody surface is transferred to another surface. This type of pattern may indicate an area where the assailant’s DNA is transferred to the decedent. Swipe patterns are similar to transfer patterns, but the transfer pattern is directional. Directionality may be seen as pattern feathering at the edge where movement ended. Wipe patterns are similar to swipe patterns, except that the wet blood isn’t transferred; it is already present as another object moves through the stain.
DNA analysis begins by extracting DNA from samples of blood, hair, saliva, semen, or tissue. This is, in scientific terms, a simple procedure, but problems may occur due to poor quality or small amounts of samples. By using special techniques and careful analysis, it is possible to separate the DNA of several people, or called “mixed of DNA” but the results are often insufficient for its conclusion.
The tools of molecular biology now enable forensic scientists to characterize biological evidence at the DNA level. These DNA typing techniques and their genetic markers are more sensitive, more specific, and more informative than the available battery of protein markers. Currently, the methods available to the forensic scientist include restriction fragment length polymorphism (RFLP) typing of a variable number of tandem repeat (VNTR) loci and amplification of the number of target DNA molecules by the polymerase chain reaction (PCR) and subsequent typing of specified genetic markers. Any material, including a hair follicle that contains nucleated cells potentially can be typed for DNA polymorphisms. There are a few reports of successful DNA typing of hairs, but these hairs usually contain sheath material. However, telogen phase hairs contain very little quantity of DNA such that most DNA markers cannot be detected, even with the use of PCR.
When sexual assault is alleged, the perpetrator’s pubic hair provides a link between the victim and the perpetrator. Taken alone, it does not prove the allegation. In concert with other evidence, however, it may prove that the sexual assault was, indeed, perpetrated by a certain individual. Likewise, dirt, paint chips, or blunt force injuries may link the victim to a scene or weapon. Such evidence may also lead investigators to discover the scene location or the object used as a weapon. For instance, a patterned injury of a belt buckle, may lead to the actual belt used and possibly to its owner.
Semen comprises seminal fluid with or without the presence of spermatozoa. Samples containing spermatozoa are rich in DNA and DNA analysis of such samples, where sperm are visible, is nearly always successful using polymerase chain reaction (PCR) techniques. A differential lysis treatment is commonly used on samples of this type in order to separate the female epithelial material from the spermatozoa, thus simplifying the interpretation of the resultant DNA profiles.
Saliva is a secretion of the mouth that is important in digestion and comprises cells and secretions from the salivary and parotid glands. Saliva has a high proportion of water and a low level of dissolved substances and cellular material, which can make it difficult to locate visually. Saliva is commonly encountered as a source of DNA evidence.
DNA extraction has two main aims: first, to maximize the yield of DNA from a sample and in sufficient quantity to permit a full DNA profile to be obtained – this is increasingly important as the sample size diminishes; and, second, to extract DNA that is pure enough for subsequent analysis: the level of difficulty here depends very much on the nature of the sample. Once the DNA has been extracted, quantifying the DNA is important for subsequent analysis.
The first step in any DNA extraction method is to break the cells open in order to access the DNA within. Although DNA may be isolated by ‘boiling’ cells, this rather crude means of disrupting the cell does not produce DNA that is always of sufficient quality and purity to be used in downstream analytical techniques such as polymerase chain reaction (PCR) amplification. DNA isolated by simple boiling generally fails as a substrate for further analysis because it has not been sufficiently separated from structural elements and DNA-binding proteins, and these impurities compromise downstream procedures. In order for DNA to be released cleanly, the phospholipid cell membranes and nuclear membranes have to be disrupted in a process called lysis, which uses a detergent solution (lysis buffer), often containing the detergent sodium dodecyl sulfate (SDS), which disrupts lipids and thus disrupts membrane integrity. Lysis buffer also contains a pH-buffering agent to maintain the pH of the solution so that the DNA stays stable: DNA is negatively charged due to the phosphate groups on its structural backbone, and its solubility is charge-dependent and thus pH-dependent. Proteinases, which are enzymes that digest proteins, are generally added to lysis buffer in order to remove proteins bound to the DNA and to destroy cellular enzymes that would otherwise digest DNA upon cell lysis. The lysis procedure sometimes calls for the use of heat and agitation in order to speed up the enzymatic reactions and lipid solubilization.
To learn more about how forensic science is used in crime scene investigation, watch this video: forensic science and crime scene investigation .
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Expert Testimony
The court determines the expert, ex officio, or at the request of the parties, and in the case of civil proceedings, the party has the possibility to propose the presentation of evidence by expert testimony.
An expert is a person invited to the court using their expertise, submit their present observations or findings and opinion on the facts that may be relevant to determining the truth of the allegations that are the subject of proof.
The term “expert” means an expert whose professional (not jurisprudence) knowledge helps resolve legal issues. A lawyer is obliged to consult with an expert witness on any matter for which there is no solution on professional competence. Thus, the expert may be a member of each profession: engineer, sculptor, compositor, an art historian, but also a doctor. The doctor is called upon as an expert in all cases where the subject of discussion physical or mental health, or their death.
The Court will take the evidence by expert testimony when to establish or clarify any facts necessary expertise which the court does not have.
Before the start of expertise, the expert witness will be called an expert to study the subject of his testimony carefully to accurately present everything he knows and finds, and to present his opinion impartially and in accordance with the rules of science and the skills. It will be particularly alert to perjury is a criminal act too. The court before which the procedure is managed by expert testimony, expert shows items that will study, puts his questions and seek explanations on its findings and opinion. An expert may be given clarifications, and he may be allowed to review documents. An expert may propose that evidence be presented or acquire objects and data that are of importance to the opinions and findings. If he is present at the crime scene investigation, reconstruction, or other investigative proceedings, the expert may propose that certain circumstances be clarified or that the test person asked certain questions.
To learn more about the role of an expert witness, watch this video: what is an expert witness .
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Responsibility of Forensic Experts
Contemporary law enforcement has greatly expanded its ability to solve crimes by the adoption of forensic techniques and procedures. Today, crimes often can be solved by detailed examination of the crime scene and analysis of forensic evidence. The work of forensic scientists is not only crucial in criminal investigations and prosecutions, but is also vital in civil litigations, major man-made and natural disasters, and the investigation of global crimes. The success of the analysis of the forensic evidence is based upon a system that emphasizes teamwork, advanced investigative skills and tools (such as GPS positioning, cell phone tracking, video image analysis, artificial intelligence, and data mining), and the ability to process a crime scene properly by recognizing, collecting and preserving all relevant physical evidence.
Recognition of physical evidence is a vital step in the process. If potential physical evidence is not recognized, collected or properly preserved and tested, the forensic value of the evidence may be greatly reduced or even lost forever. Numerous routine and high profile cases have demonstrated the harsh reality that despite the availability of current crime scene technologies, specialized equipment, and sophisticated forensic laboratory analysis, the effective utilization of physical evidence in crime-solving is only as good as the knowledge and integrity of the crime scene personnel and the objective legal system that supports those functions. In some cases, evidence has been falsified or results tainted, misleading the justice system.
Social and ethical implications of computers are fast deep and irreversible. Mankind stepped into the information age - an age of sharing knowledge and integration of the system where the information quality and speed of decision-making decisive parameters. Traditional jobs from the industrial era disappear and reappear as new, automatized jobs with contemporary technologies. Computers more than any other technologies affect, directly or indirectly, developments in telecommunications, genetic engineering, medicine, and atomic physics. The biggest changes in daily life brought results like developing artificial intelligence, multimedia, and robotics. However, it is equally important to understand all the potential risk factors of the coming changes in the social and personal life, which bring modern Internet and other related technologies, such as: invasion of privacy, high-tech crime, and the difficulties of maintaining security information, protection of intellectual property in the digital environment, the inevitable bugs in the development of complex software, automatization and dehumanization of labor, abuse information for the realization of political and economic power, too much dependence on complex technology, blurring the physical reality with virtuality and create even greater depending on the people of the computer and the Internet and the appearance of bio-digital (nano) technology, where researchers are trying to develop a computer instead of electronics used biological cells as the supporting technology.
How can we connect forensics, artificial intelligence, and high-tech crime? Intelligent forensics is an inter-disciplinary approach, which makes use of technological advances and applies resources in a more intelligent way to solve/help an investigation. Intelligent forensics encompasses a range of tools and techniques from artificial intelligence, computational modeling, and social network analysis in order to focus digital investigations and reduce the amount of time spent looking for digital evidence.
The application of intelligence in computer forensics investigations takes on a number of components at various stages of the investigation life cycle—the gathering of digital evidence, the preservation of digital evidence (evidential integrity and evidential continuity), the analysis of digital evidence, and the presentation of that evidence. In each of these stages, the skill and knowledge of the computer forensics investigator is fundamental to the success of any investigation. However, it is hoped that the application of artificial intelligence to digital forensic investigations will provide a useful set of tools to the investigator to address complex issues and more importantly will address the issues associated with speed and volume (size of data being investigated rather than the backlog of cases which is a separate issue) of digital investigation cases, by identifying the most relevant areas for investigation and excluding areas where results are less likely. This approach has been used previously to a certain extent by the application of hash algorithms to eliminate dormant files and “static” systems files from digital investigations.