Fingerprints are the very basis for criminal identification and conviction in every police agency on earth. Fingerprint evidence represents one of the most important pieces of evidence found at the scene of a crime, and can be used to determine the steps that the suspect took while committing the crime, but also has the ability to rule out suspects, or to eventually lead to the offender. The idea that no two individuals can have identical fingerprints is accepted by the courts and can lead to a fingerprint being the single piece of evidence in a crime that will lead to a conviction. Although, in recent years, the reliability and validity of using finger printing as evidence has been questioned by a variety scientists and also the media.
Correctly identifying the type of surface expected to have a fingerprint present is a vital step in successful devel¬opment. Surfaces are generally separated into only two groups: porous and nonporous. This separation is requires the forensic scientist to select the proper technique or reagent to use on the surface in order to correctly find and use the print in evidence. Porous substrates are mostly absorbent and include materials like paper, cardboard, wood, and other forms of cellulose material. Fingerprints which are left onto these materials get absorbed and can pose a challenge to retrieve if the correct technique is not used. Amino acids in the print are able to be detected because the amino acids remain fixed when absorbed and are not easily damaged (Almog, 2001, p 178). Nonporous surfaces do not absorb any amino acids from the fingerprint these surfaces repel moisture and often appear polished. They include glass, metal, ceramic, plastics, lacquered or painted wood, and rubber. Latent pri...
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...ts from dark surfaces. (Menzel, 1999, pp 62–65).
For development of latent prints on porous surfaces such as paper and cardboard a chemical called ninhydrin is used. At least 14 amino acids may be present in fingerprint residues (Knowles, 1978, pp 713–720; Hier et al., 1946, pp 327–333). To produce the best-developed fingerprint, the ideal reagent must be nonspecific to a particular amino acid (i.e., reacts well with all). Ninhydrin is one of many chemicals that acts as a nonspe¬cific amino acid reagent and is, therefore, very suitable for fingerprint development (Champod et al., 2004, p 114; Almog, 2001, pp 177–209). The Ninhydrin reacts to the amino acids in the latent print and turns the print purple, which is now known as Ruhemann’s purple. This chemical is very useful in collecting prints off paper as it develops in a fume hood with no loss of document detail.
To start with, the first separation technique we performed on the heterogeneous mixture was filtration. According to our observations of the residue, we believed graphite was one of the substances in the mixture. Graphite, a known ingredient used in pencils, is black or dark grey in color, like the dark spots on the filter paper (Figure 1B), and has the ability to leave marks on paper and other objects. Of the potential components given to us, only graphite possessed the ability to make a mark on other surfaces. This was supported by the smudges left behind on our finger and filter paper (Figure 1A, bottom filter paper) when we touched the residue.
PURPOSE: The purpose of the experiment is to determine the specific types of pigments found in water-soluble marker pens by using paper chromatography and water as a solvent.
At the initial stage of the investigation all the visible evidence is to be observed from the latent impression perspective. At this stage only the physical evidence is taken into account. The objects can be divided into porous and non-porous surfaces from the imprint ability preservation perspective. It is advisable to send all the available evidence to the laboratory expertise, though the non-porous substances...
Nowadays, DNA is a crucial component of a crime scene investigation, used to both to identify perpetrators from crime scenes and to determine a suspect’s guilt or innocence (Butler, 2005). The method of constructing a distinctive “fingerprint” from an individual’s DNA was first described by Alec Jeffreys in 1985. He discovered regions of repetitions of nucleotides inherent in DNA strands that differed from person to person (now known as variable number of tandem repeats, or VNTRs), and developed a technique to adjust the length variation into a definitive identity marker (Butler, 2005). Since then, DNA fingerprinting has been refined to be an indispensible source of evidence, expanded into multiple methods befitting different types of DNA samples. One of the more controversial practices of DNA forensics is familial DNA searching, which takes partial, rather than exact, matches between crime scene DNA and DNA stored in a public database as possible leads for further examination and information about the suspect. Using familial DNA searching for investigative purposes is a reliable and advantageous method to convict criminals.
Crime is a common public issue for people living in the inner city, but is not limited to only urban or highly populated cities as it can undoubtedly happen in small community and rural areas as well. In The Real CSI, the documentary exemplified many way in which experts used forensic science as evidence in trial cases to argue and to prove whether a person is innocent or guilty. In this paper, I explained the difference in fingerprinting technology depicted between television shows and in reality, how DNA technology change the way forensics evidence is used in the court proceedings, and how forensic evidence can be misused in the United States adversarial legal system.
Another discrepancy between actual forensics and how it is portrayed in the media is the availability of information in databases. There is only a small percentage of the entire population’s fingerprints or DNA samples stored within databases such as the Integrated Automated Fingerprint Identification System (IAFIS). This makes finding a match between a DNA sample or fingerprint difficult, as a match would only be found if the person’s information was already stored within the database. If there is no match previously stored in a database, the fingerprint or DNA sample could be potentially rendered useless within a trial. Typically, in order to perform an analysis, investigators must already have a suspect in mind and request a DNA or fingerprint sample from him or her. If the suspect does not want to provide one however, the sample collected as evidence may not count as valid. The CSI effect creates an idealized image that all crimes can be solved with a hair or drop of blood, but this is not always the case in real life.
Although physical proof is vital in police investigations, when there's depleted evidence present at the crime scene, offender profiles are often created to lead law enforcement towards physical evidence and possible suspects. This is important as physical evidence such as fingerprints, fibres and biological evidence, aids to establish the guilt or innocence of potential suspects, although criminal profiling can be used in court it itself is not evidence but built of evidence from the crime scene to establish
Contextual information also affects the human comparative part of fingerprint analysis, in ways that alter the matching of the same fingerprints, years apart; however, when contextual information is provided, it actually helps 20% of forensic technicians, but that still leaves 80% hindered by contextual information (Dror et al, 2006). Contextual information affects the psychological aspects of perception and problem-solving, in a way that can obscure information that does not support the context, and it can even affect how forensic technician’s view and handle forensic evidence (Bernstein et al, 2013). However, there are some advantages of contextual information, because it can give the forensic division a mental shortcut, saving time and money; however, these shortcuts lead to inaccurate and biased conclusions. This essay has shown that contextual information creates erroneous mistakes and prejudiced results in forensic investigations. A possible way to remove the negative effects of contextual information is to have the forensic technicians, not know the context of the crime so that they do not
The criminal justice system has changed a lot since the good old days of the Wild West when pretty much anything was legal. Criminals were dealt with in any fashion the law enforcement saw fit. The science of catching criminals has evolved since these days. We are better at catching criminals than ever and we owe this advancement to forensic science. The development of forensic science has given us the important techniques of fingerprinting and DNA analysis. We can use these techniques to catch criminals, prove people's innocence, and keep track of inmates after they have been paroled. There are many different ways of solving crimes using forensic evidence. One of these ways is using blood spatter analysis; this is where the distribution and pattern of bloodstains is studied to find the nature of the event that caused the blood spatter. Many things go into the determination of the cause including: the effects of various types of physical forces on blood, the interaction between blood and the surfaces on which it falls, the location of the person shedding the blood, the location and actions of the assailant, and the movement of them both during the incident. Another common type of forensic evidence is trace evidence. This is commonly recovered from any number of items at a crime scene. These items can include carpet fibers, clothing fibers, or hair found in or around the crime scene. Hairs recovered from crime scenes can be used as an important source of DNA. Examination of material recovered from a victim's or suspect's clothing can allow association to be made between the victim and other people, places, or things involved in the investigation. DNA analysis is the most important part of forensic science. DNA evidence can come in many forms at the crime scene. Some of these forms include hair; bodily fluids recovered at the crime scene or on the victim's body, skin under the victim's fingernails, blood, and many others. This DNA can be the basis of someone's guilt or innocence; it has decided many cases in the twentieth century. As the times continue to change and the criminals get smarter we will always need to find new ways to catch them. Forensic science is the most advanced method yet, but is only the beginning. As the field of science grows so will the abilities of the
Once a crime has been committed the most important item to recover is any type of evidence left at the scene. If the suspect left any Deoxyribonucleic acid (DNA) at the crime scene, he could then be linked to the crime and eventually charged. A suspect’s DNA can be recovered if the suspect leaves a sample of his or her DNA at the crime scene. However, this method was not always used to track down a suspect. Not too long ago, detectives used to use bite marks, blood stain detection, blood grouping as the primary tool to identify a suspect. DNA can be left or collected from the hair, saliva, blood, mucus, semen, urine, fecal matter, and even the bones. DNA analysis has been the most recent technique employed by the forensic science community to identify a suspect or victim since the use of fingerprinting. Moreover, since the introduction of this new technique it has been a la...
The three different main types of fingerprints are Loops, Arches, and Whorls (Jackson 1). Henry Faulds is known as the Father of Fingerprints and developing fingerprints (Jackson 1). His discovery of fingerprints has made a huge impact not only in his time but, in Modern Crime Scene Investigation (Jackson 1). Without fingerprinting, it would be very difficult to convict criminals of crimes and very hard to try to process information. Crime Scene Investigators make a huge impact in Forensic Science. We need CSI workers, without them people could only imagine what crime would be like not only in our community, but in our
one may assume that a detailed investigation of William’s bedroom began before a search warrant was obtained or consent to search was given. Therefore, when crime scene investigators began to process William’s bedroom, any evidence found, including the bloody fingerprint that was not in plain sight but developed using an amino acid stain and an argon laser, would not be admissible in court.
...A. Maria, Ruth M. Robin. (2009). Latent prints: a perspective on the state of the science. Forensic Science Communications. 11.4.
Strands of human hair situated at the crime scene gives exceptionally solid sign that an individual was at that area, yet it can likewise be useless if the fibres were found outside and, subsequently subject to the elements such as wind, and if the full length of the strand is not present (Dasgupta, 2007). Hair without anyone else 's input is essential, but rather the most imperative DNA evidence connected with hair fibres originates from the cellular material at the root of the hair strand. In a way, the microscopic particles of follicle give the most solid proof. The protein called keratin is the key substance that goes with the follicle, and that gives the best distinguishing proof. On the off chance that the hair is taken off by the root, for example that could happen when an individual is guarding him or herself against an attacker, then the hair fibres are essential (Innes, 2000). Hair that does exclude follicular material is a great deal less dependable. Hair fibres that do exclude keratin are helpful in distinguishing a category of individual into which a suspect may fit, however they are not complete evidence that the hair originated from the suspect (Innes, 2000). Therefore, personally, hair fibres are less important than fingerprints and DNA evidence acquired from saliva or blood. Fingerprints are not DNA evidence, but still they are extremely dependable types of evidence. DNA obtained from bodily fluids, in any case, is the most profitable type of evidence
Physical evidence is additionally important in every criminal investigation because too often witness accounts are sometimes biased or unreliable. Physical evidence such as trace evidence, DNA, and fingerprints may objectively attach one or more persons to a victim or suspect to a crime. Favorably, physical evidence can also demonstrate inestimable for exonerating an innocent suspect. Laboratory members and criminal investigators should perform together to resolve the biggest portion of evidence to institute the right suspect for a strong prosecution. Willingly, investigation officers should aggressively contact laboratory personnel when questions arise about the cases because DNA evidence is sensitive.