‘’Forensic evidence is infallible’’. Discuss PDF

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‘’Forensic evidence is infallible’’. Discuss Deoxyribonucleic acid is a chemical structure that carries genetic information in every living organism. One of the most important goals and tasks of forensic science is to develop a reliable and effective method of identifying perpetrators of crimes based on those left behind. This essay will explain the PCR amplification method and draw on its advantages in identifying forensic evidence especially DNA samples. Forensic evidence has been described as a reference to the application of scientific techniques in order to detect crime by Peter Joyce. It developed from an approach that originally focuses on meticulous observation of the crime scene and therefore enabled a search for evidence that might lead to the offender. The evidence can contain different materials such as fingerprints, footprints, bullets and trace evidence including semen, hair, saliva, skin and blood. Throughout the essay DNA evidence will be discussed in detail with a strong emphasis on ‘’Touch DNA’’. Infallible means incapable of being wrong but is forensic evidence entirely flawless? Secondary transfer of DNA and the advancement in technology proves that forensic evidence is in fact fallible and illustrated by many case examples only strengthens the potential room for error. There are also many internal and external factors which affect the accuracy of DNA which will be looked upon in this essay. This essay shall conclude on the strengths of forensic evidence however, it will prove that it has a potential to be fallible as illustrated by many cases and studies. Forensic evidence effectiveness and contribution has been assessed through The joint FSS/ACPO report ‘’Using Forensic Science Effectively’’ (ACPO/FSS 1996). The report classified evidence into one of three categories; inceptive which was the evidenced that pointed directly to an unknown offender, corroborative which tends to confirm an existing hypothesis and mandatory which is evidence necessary to satisfy a specific legal requirement (ACPO/FSS 1996).During the 1970s studies done in the US showed that

forensic evidence is a tool to either confirm a suspicion or to eliminate a suspect. It was much less frequently used to develop suspect sets along inceptive lines. ‘’Apart from a few exceptional cases...the police turned to the FSS because their investigations needed to be deepened if they were to be sure of gaining a conviction. There were, for instance, hardly any cases where the police had identified a suspect on the basis of fingerprint marks’’(Ramsay, 1987 p13), the study carried out by Ramsey shows that in 79% of the cases the suspect was identified before their fingerprints and DNA was sent for testing. Advocates of forensic DNA testing from the outset of biochemical methods claimed that DNA testing is infallible. In publications, advertising materials and expert opinions, it was maintained that DNA tests either present the correct result or do not show it at all. This theory was even more strongly supported in 1996, when the National Research Counsel in the United States in one of its reports on DNA testing in court stated: "One should not doubt both the reliability and the validity of properly collected and analysed DNA samples " This claim was further strengthened in the social image by the news about the purification of previously convicted complaints, thanks to DNA research. It was shown how wrongly convicted persons were released from prisons, while those guilty were brought to justice. The infallibility theory proved to be helpful in determining the acceptability of forensic DNA tests and supporting the creation of government DNA databases. The "infallibility" of DNA testing has become a widely accepted fact. There are several cases where forensic evidence was the key to tracing back to the offender such as the 1998 murder case of Anna Palmer. The 10 year old was murdered outside her front door in Salt Lake City, USA. There was very little evidence in the case, no witnesses and no suspects. In 2009, forensic analysts assisted in the case and examined the girls fingernails for DNA not belonging to her. The DNA was matched to Matthew Brock who lived near Anna Palmer at the time of the murder. He was already serving 10 years in

prison for a sex related crime and in 2011 he pled guilty to the murder of Anna Palmer and is now serving a life sentence. This shows that despite 11 years after the crime DNA evidence was still traceable and lead to a successful ending to the case where a suspect was found guilty. Without DNA evidence being examined from under Anna Palmer’s fingernails, there could be a possibility that Matthew Brock would never been found guilty of this crime. Another case which highlights the strength of forensic evidence and its infallibility is the Stephen Lawrence murder in 1993. Despite the 90s forensic techniques being less developed at the time scientists were able to go back to the evidence in 2012. Due to the advancement in technology the forensic scientists were able to magnify a 0.05mm blood stain left on Lawrence’s jacket using 40 times magnification which matched his DNA. Back in 1993, testing on such small samples was impossible and would not be looked at as evidence. The technological advancement also helped to identify the hair left on David Norris’s jeans which also matched Stephen Lawrence’s DNA profile. Peterson, Mihajlovic and Gilliland (1984) undertook a major study which examined 2,700 cases drawn at random from US police files. The study found that cases which involved forensic evidence (1,600) had higher percentages of being solved compared to the ones that lacked physical evidence. Burrows et al., 2005 also conducted a study which has shown that 68% of suspect identification came from fingerprints and 17% from DNA. The study has concluded that forensic evidence provides a first link between a offender and a crime in 45% of cases with DNA accounting for the highest link connection. However, Peterson et al. (1986, 1987) highlights that the conviction rate of cases where forensic evidence was found was not was not significantly higher than cases without forensic evidence.Although forensic evidence has room to make error it is a substantial part of investigations which in many cases proves to be infallible and leads to the right suspect.

In 1997, Roland A. H. van Oorschot raised that secondary DNA contamination transfer can be a problem. Legal experts dismissed this possibility due to the outside conditions of a laboratory and the rarity of secondary transfers. However , ’’Experiments done in realworld conditions seemed to support this, and concluded that secondary DNA transfer would have little impact on interpretation of the genetic profile.’’ Roland A.H van Oorschot(1997). The new DNA kits can generate a full genetic profile from 100 pictograms of DNA and such sensitiveness is not explained in court therefore it is the jurors nature to assume that the defendant was at the crime scene. The advancement of Forensic Science techniques has lead to the ability of obtaining a DNA profile from a tiny amount of cells which means that secondary transfer is not a theoretical risk anymore. ‘Touch DNA’ means that a genetic profile is generated in a laboratory from very little skin cells left in a fingerprint. Due to ‘’touch DNA’’ sample being low in amounts of DNA, direct PCR amplification method is used to extract as much DNA as possible. This is a method in which a sample is added directly to an amplification reaction without being subjected to prior DNA extraction, purification, or quantification. The method allows for maximum quantities of DNA to be targeted and minimises the potential of an error being made and the sample being contaminated. Despite the method maximising the information being obtained from a sample, it can also result in more mixtures being found which require laboratory interpretation. ‘’Touch DNA’’ gives an impression to the jury that the biological material found on an object is due to the defendant coming directly into contact with it. However, University of Indianapolis, Indiana, USA (2015) highlights that forensic evidence can be highly unreliable and found that it is very straightforward for innocent people’s DNA to be transferred onto different surfaces that they have never come into contact with. The amount of DNA transferred depends on various factors such as the person’s perspiration, propensity to shed epithelial cells, frequency of hand washing or surface

touched.Therefore a person does not have to come into direct contact with an object in order to leave their DNA behind, this is known as secondary transfer. Secondary transfer could potentially link people at crime scenes they have never visited. Buckingham et al study demonstrates that background DNA is a component of DNA present on an individuals hand, and when an object has been touched by multiple individuals, the last handler is not always the major contributor . This indicates that DNA profile interpretation may remain complicated and increases the potential of wrongly placing an individual at a crime scene. Cale et al (2015) has revisited DNA transfer using more current and sensitive technology where the chances of obtaining results from low quality samples could be increased. The study evaluates wether it is the sensitivity that could increase the detection of interpretable secondary DNA transfer profiles. Participants were asked to have hand to hand contact and after two minutes they were immediately handed knives. The knives were then swabbed and results indicated that secondary DNA transfer was detected in 85% of the samples. In five samples, the secondary contributor was either the only contributor or the major contributor identified despite never coming into direct contact with the knife. This study demonstrates the risk of assuming that DNA recovered from an object resulted from direct contact. As demonstrated in the Lukis Anderson case (2013) forensic evidence proves to fallible. Anderson was arrested in 2013 in California and was charged with murder after his DNA was found under the victims fingernails. He was intoxicated and in hospital when the murder took place. The same paramedics who took Anderson to hospital were the ones that responded to the murder. The charges were eventually dropped due to the paramedics being covered in Anderson’s DNA, which they transferred onto the murder victim.

Another case that demonstrates that secondary transfer of DNA is a very high risk is the German ‘’Phantom of Heilbronn”. In this case a woman was linked to 40 violent crimes, where 6 of them were murders. The crimes included theft, murders and brutalities dating back to 1993. The only thing that linked the crimes was the DNA retrieved at each crime scene which belonged to the same woman. There was no pattern in the woman’s crimes and some of the victims described her looking like a man. In March, 2009 the German police concluded that the phantom never existed and the DNA was present on the cotton swabs prior to being used to collect DNA samples. All the cotton swabs used during the crime cases that the woman was supposedly responsible for, were produced at the same factory at which the woman worked. Although the cotton swabs were properly sterilised and all the procedures were followed, they still became contaminated with human cells. There are a number of internal and external factors which affect forensic evidence material. Internal and external factors can lead to the acceleration or complete degradation of material originating from humans, which makes it impossible to carry out effective analysis. External factors include: weather at the scene of the incident (increased air temperature, high humidity, intense precipitation, UV radiation) environmental conditions (pH of the substrate including different acids, feeding organisms on organic matter, surroundings with an atmosphere rich in detergents and other chemical agents) and factors directly related to a given event (high temperature of flames, negative effect of seawater after sinking a ship, thermal impact after a plane crash, etc.). The quality of the protected DNA may also be adversely affected by internal factors (conditions of protection, storage and the transport of biological material itself) and factors associated with inappropriate behaviour at the scene (eg extending the time needed for the inspection, inappropriate protection of the site, lack of applying health and safety rules, direct irradiation with too strong source of ultraviolet light, lack of sterile and appropriate equipment, including sterile packaging). Also when looking at retrieving DNA evidence the

factors related to inadequate storage and transport, material retention under inappropriate conditions, improper packaging, non-use of refrigerators or transport chillers, sterility of the vehicle interior need to be considered. Due to the above factors, sometimes it is not possible to carry out a standard DNA analysis requiring from 500 pg to 2 ng of DNA, which corresponds to 75-300 human cells. Because the external and internal processes mentioned above lead to DNA degradation they significantly impede the interpretation of the genetic profile due to the formation of artefacts in the form of uneven amplification of heterozygous alleles. In conclusion, forensic evidence is not infallible. R.H Van Oorschot (1997) highlighted that secondary transfer of DNA can be a problem , this later proved DNA’s fallibility. Supported by many cases such as the ‘’Phantom of Heilbronn’’ , secondary DNA transfer become a bigger risk when examining forensic evidence. Cale et al (2015) study shows that secondary DNA transfer was present in 85% of the samples used during his study. Overall, forensic evidence is not infallible, there is room for error and it does come down to many factors that affect the samples from crime scenes. Internal and external factors need to be considered prior to obtaining a match from fingerprints and DNA due to there being a possibility that the material has become degraded. However, due to new DNA kits and methods such as PCR being developed it is much easier for forensic scientists to identify evidence samples including ‘’touch DNA’’. PCR method makes it possible to identify genetic profiles from low amounts of cells contained in ‘’Touch DNA’’.Forensic evidence has allowed many cases to be closed and the PCR method proved to be infallible in the Stephen Lawrence case despite it being revisited many years later. Forensic evidence remains one the the major links between a offender and a crime however, such evidence can place innocent people at crime scenes they have never visited due to secondary transfer. "...