DNA Analysis

Since its introduction in 1985, DNA typing has revolutionized the science of forensic testing; presently, this kind of testing has become commonly used when determining an individual’s predisposition to a given disease, paternity, embryonic health and innocence or guilt. This field of forensic science has considerably improved the ability of agents tasked with the responsibility of law enforcement to match perpetrators to the scenes of crime. A huge number of cases have been solved and suspects who are innocent freed; at the same breath, the guilty persons have been brought to book thanks to DNA which is more or less a biological witness, and a silent one at that at the actual scene of the crime (DNA Initiative).This paper seeks to discuss in detail the history, changes and theories, successes and failures of forensic science. The paper will also highlight the advances of technology and limitation of evidence. The importance and limitations of forensics to police work in the future will also be discussed.

History of Forensic Science

The history of forensic science dates back hundreds of years ago, notable developments, however, came about during the 1950’s and it is still developing nowadays. In 1950, in Chicago, Illinois, the American Academy of forensic Science was formed. This group subsequently initiated the publication of a journal that came to be known as the Journal of Forensic Science. M. Cutbush and a group of other scientists were the first to describe the Duffy blood group system. The same year, August Vollmer, Berkeley’s chief of police, set up the school of criminology which was based at the University of California at Berkeley. Max Frei-Sulzer presided over the major of criminalistics within the school. .In 1951, F.H. Allen and a group of his colleagues were the first to describe the Kidd system of blood grouping. In 1953, Kirk published one of the premier crime investigation texts which also dealt with criminalistics; this publication was unique in that it encompassed theory as well as practice. In 1954, R.F. Borkenstein, who at that time was the captain of the Indiana State Police came up with the Breathalyzer whose application was in the field of sobriety testing (Rudin & Inman, 2002).

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In 1958, A.S. Weiner and a group of his colleagues pioneered the use H-lectin to determine positively O blood type. In 1959, Hirshfield described the polymorphic characteristic of group specific component also known as GC. The following year in Canada, Lucas came up with gas chromatography (GC) in the identification of petroleum based products; at the same time, he worked on the potential limitations in gasoline’s brand identity. In the 1960’s, Maurice Muller, a Swiss scientist, in a bid to determine species, adapted the use of Ouchterlony antibody-antigen test. In 1963, D.A. Hopkinson and a group of scientists, he was working with, became the first to identify the polymorphic nature of erythrocyte acid phosphatase (Rudin & Inman, 2002).

In 1964, N. Spencer together with his colleagues was the first to describe the polymorphic nature of phosphoglucomutase which is a red cell. A year later, R.A. Fildes and H. Harris became the first to observe and describe the polymorphic nature of adenylate cyclase, which is a red cell. The same year, Brian J. Culliford and Brian Wraxall came up with the immunoelectrophoretic technique which was used for haptoglobin typing of blood stains . Culliford also started the development of gel based methods when testing for isoenzymes in blood stains that are dry. In 1974, J.Wessel, P.Jones, Q.Kwan, R.Nesbitt and E.Rattin who were working at the Aerospace Corporation developed the SEM-EDX technology which used scanning electron microscopy combined with X-rays that were electron dispersive to detect gunshot residue (Rudin & Inman, 2002).

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In 1975, the Federal Rules of Evidence were enacted by the Congress of the United States as a statute. In 1977, the FBI initiated their Automated Fingerprint Identification System which also had the first scans of fingerprints that were computerized. In 1986, DNA was first used to solve a crime in the English midlands. In 1987, DNA was introduced in an American criminal court for the first time; the analysis was done by Lifecodes and it led to the conviction of Tommy Andrews for a number of sexual assaults in Florida. In 1991, Walsh Automation Inc. in collaboration with the Bureau of Alcohol, Tobacco and Firearms developed the Integrated Ballistics Identification System for the purposes of comparing the marks left on cartridge cases, fired bullets as well as shell casings. In 1994, Roche Molecular Systems introduced a set of DNA markers. 1996 marked a milestone in forensic testing when for the first time in a U.S. court as evidence was admitted mitochondrial DNA typing. In 1998 the FBI DNA database was set up; it of aided Interstate Corporation in linking crimes (Rudin & Inman, 2002).

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Past and Present Techniques

In the past, forensic development was considerably slow, however, since the mid-80s the number of techniques has considerably increased. In 1985, the field of forensic analysis witnessed a breakthrough of a kind. VNTR’s which refers to the variable number of tandem repeats showed a greater degree of variability in among individuals than the other systems that were previously used and, as a consequence, it started being used for the purposes of forensic studies. Though they are still being used, they are being replaced albeit rapidly by STR’s or short tandem repeats (National Institute of Justice, 2000).

Given the great variability in as far as the variability of polymorphisms of DNA is concerned, scientists are now able to offer greater support when they conclude that DNA from a given crime scene matches the suspect`s one. Before, a suspect could be excluded; furthermore, evidence for inclusion was comparatively weaker. This can be explained by the fact that back then, the chances of a coincidental match tended to be larger. Though, the evidence that a pair of DNA samples are from the same individual still is probabilistic, given the barrage of genetic markers, the chances that the pair of matching profiles are from the same individual more or less approaches certainty. Thanks to DNA testing, over 70 individuals who had previously been convicted of a variety of capital crimes have been exonerated; many of them had served extended prison terms (National Institute of Justice, 2000).

Mitochondrial DNA as the name suggests is found in the mitochondria. These are minute organelles found in the cell and do not have an association with nuclear chromosomes; they are not transmitted by the sperm but by the egg. This is, therefore, useful when studying the relations of people through the female line. Each cell has numerous mitochondria; this means that it is possible to analyze DNA of a smaller amount as opposed to if it were the case that the DNA was chromosomal, for instance DNA found in a shed hair follicle. CODIS, which refers to the Combined DNA Index System is a database of DNA profiles which is electronic and is administered by the Federal Bureau of Investigations (National Institute of Justice, 2000).

Restriction Fragment Length Polymorphism or RFLP is a technique that analyzes the actual lengths of DNA fragments. This is done by digesting a sample of DNA with a special enzyme. It was one of the premier applications in as far as DNA analysis for the purpose of forensic investigation is concerned. However, it does not work well on samples that may be degraded in any way for instance mold or dirt (National Institute of Justice, 2002).

Polymerase Chain Reaction or PCR is applied when the need to make millions of exact copies of the DNA of a given sample arises. This technology has the ability to amplify tiny samples of biological DNA. This is ideal as it makes it possible for forensic scientists to analyze samples that may be highly degraded. It is important, however, to exercise a lot of caution to protect the sample from contamination by other biological materials in the process of identifying, collecting as well as preserving the sample material (National Institute of Justice, 2002).

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