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The role of forensic scientists in criminal investigations
DNA as an investigative tool
Dna crime investigation
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. 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 large number of individuals released or convicted of crimes based on DNA left at the crime sceneDNA is the abbreviation for deoxyribonucleic acid. DNA is the genetic material found in cells of all living organisms. Human beings contain approximately one trillion cells (Aronson 9). DNA is a long strand in the shape of a double helix made up of small building blocks (Riley). There are four types of building
The repeat segments are cut out of the DNA strand by a restrictive enzyme that acts like scissors and the resulting fragments are sorted out by electrophoresis (Saferstein 391). However, there are some drawbacks using the RFLP method in the forensic science community. The RFLP technique requires a large amount of DNA and must be of high quality and cannot be degraded (Jones). Forensic scientists and the law enforcement community determined a need for a DNA profiling method that could be used on smaller DNA samples. Thus, the RFLP technique has been almost entirely replaced by Polymerase chain reaction. PCR or polymerase chain reaction is not a DNA typing technique, but a variety of different DNA tests (Riley). PCR duplicates and increases the quantity of a DNA strand which is beneficial to forensic scientists who are faced with little quantity of materials (Saferstein 394). The introduction of PCR-based testing in DNA analysis required scientists to switch to smaller targets that had the same repetitive variation (Jones). This is how short tandem repeat, the newest method of DNA typing,
In 1989 the National Research Council Committee on DNA Technology in Forensic Science was developed due to numerous scientific and legal issues (The Evaluation of Forensic DNA Evidence). The National Research Council’s key role was to analyze statistical and population genetic issues in the use of DNA evidence and review major alternative approaches to statistical evaluation of DNA evidence (The Evaluation of Forensic DNA, 50). Over the past fifteen years DNA profiling has made tremendous advancements and continuous improvements in the fight against violent
According to the FBI’s NDIS Statistics, CODIS has produced over 120,300 hits assisting in more than 117,800 investigations as of June 2010 (Federal Bureau of Investigations, 2010). All states collect DNA from convicted felony offenders, but many have passed bills t...
Using PCR and Gel Electrophoresis to Determine Genotype. In certain situations, it is necessary to identify DNA retrieved from a sample. When there is a small sample in need of identification, Polymerase Chain Reactions are used to multiply the DNA. in the sample in many identical samples.
Deoxyribonucleic acid (DNA) is an acclaimed extraordinary discovery that has contributed great benefits in several fields throughout the world. DNA evidence is accounted for in the majority of cases presented in the criminal justice system. It is known as our very own unique genetic fingerprint; “a chromosome molecule which carries genetic coding unique to each person with the only exception of identical twins (that is why it is also called 'DNA fingerprinting ')” (Duhaime, n.d.). DNA is found in the nuclei of cells of nearly all living things.
DNA evidence should not be collected from suspects as a matter of routine unless the information is relevant to a specific crime in question. For example, it would appropriate to obtain a DNA sample from a suspect where DNA evidence is left at the scene of a crime and the suspect's DNA in needed to prove the suspect's involvement.
DNA (Deoxyribonucleic acid) is a molecule found in in the nucleus of all cells in the body which carries our genetic information. DNA is found in the form of chromosomes, with a total of 23 pairs in the human body1. DNA holds the genetic coding for all our characteristics, i.e. our eye colour, body shape, and how we interact with others on a daily basis.
Studies have shown that “eyewitness misidentification is the single greatest cause of wrongful convictions nationwide [contributing] […] [to] more than 75% of convictions overturned through DNA testing” (American Civil Liberties Union). The first situation resulting in the misidentification, was made when the police rounded up six men according to the ...
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.
Thompson, W. C. (1996). DNA Evidence in the O.J. Simpson Trial. University of Colorado Law Review, 827-857.
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.
On Wednesday, November 16, 2011, Katherine Stang, Aresh Kabirnavaei, and Andrew Roller, all students in the Master’s of Forensic Science program gave thesis presentations to the Forensic Seminar Class. The following paragraphs will summarize each topic.
DNA analysis is a scientific process among the newest and most sophisicated of techniques used to test for genetic disorders, which involves direct examination of the DNA molecule itself (Lyman, 2014) . Today crime labs use mtDNA analysis. This type of analysis allows smaller degraded pieces of DNA to still be successfully tested (Lyman, 2014) . There are several steps taken when analyzing DNA in forensics. When testing scientists must first isolate the DNA so it is not contaminated and can't be used. Lab technicians the take small pieces of the DNA, conserving as much as they can encase they need to test again. Once testing is done the next step is determining the DNA test results and finally there is the comparison and interpretation of the test results from the unknown and known samples to determ...
Forensic genetics has other applications . The " fingerprint " DNA represents a valuable tool for forensic science . As is the case with an ordinary fingerprint genetic fingerprint is unique to each individual (except identical twins ) . The determination involves the observation of specific DNA sequences which can be obtained from extremely small tissue samples , hair, blood or eventually left at the scene . As Fifty microliters of blood, semen or five microliters of ten roots of hairs are enough , and nozzles secretions and cells from the fetus . In addition to its use in the capture of criminals , especially rapists , the genetic fingerprints can be used to establish family relationships . People involved in the conservation of species use them to be sure that captive breeding is among individuals who do not belong to the same family .
Since DNA technology has been used there has been a high number of individuals convicted, linked or found innocent of a crimes. This technology has helped law enforcement catch suspects that may have never been found without the use of this technology. However, the research reflected that there is a need for clearer interpretations of the DNA results, better equality provided for all regardless of race or class and that errors should be reduced to prevent having cases that need to be exonerated.
DNA profiles do not consist of a person’s entire DNA sequence. Instead, scientists use short tandem repeats (STRs), a sequence of 2-6 base pairs that repeats in the genome. Short tandem repeats are useful because they can be replicated using polymerase chain reaction (PCR) amplification. Even though only a small part of the person’s DNA is included in the profile, it is unlikely to match another person’s profile. In the United Kingdom, ten STRs from different places in the genetic sequence are used to create a genetic profile, and the match probability is one-in-a-billion; however, a match is more likely to occur among relatives.
This means that the not all forms of DNA testing are being validated properly, such as; hair microscopy, bite mark comparisons, firearm tool mark analysis and shoe print comparisons. Serology (blood-typing) can also be inadequately carried out in their trial testimony (“DNA Exonerations”). Scientists are able to do these tests because DNA is unique to everyone.