Locards exchange principle essay PDF

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It is accepted within the criminal justice system that every forensic practitioner is competent in terms of qualifications and experience to fully apply Locard’s exchange principle to ensure that contamination never occurs at crime scenes or within laboratories. It can be suggested therefore that co...

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Kerry Greer AC

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The fundamentals of forensic investigation Trevor Boddy (if you are unsure who is marking the assignment insert the module leader’s name)

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Locard’s exchange principles 08/01/18

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I have read the University’s procedures on plagiarism, available in the Departmental Handbook, and accessible on the University website. I certify that this is my own work, and does not contain plagiarised, copied or duplicated material. 06/01/18

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It is accepted within the criminal justice system that every forensic practitioner is competent in terms of qualifications and experience to fully apply Locard’s exchange principle to ensure that contamination never occurs at crime scenes or within laboratories. It can be suggested therefore that contamination is never an issue when evidence is presented at court.

Critically discuss the above suggestion in terms of the forensic investigation process from crime scene to court. Reference your research using published information relating to Locard’s exchange principle, contamination of evidence, continuity of evidence and where possible relate your discussion to any miscarriages of justice or published examples of contamination of evidence.

Within the criminal justice system, it is required and expected that all forensic practitioners have a competent understanding of Locard’s exchange principle and apply it alongside up to date qualifications in order to ensure that contamination of evidence never occurs at crime scenes or laboratories. Locard’s exchange principle refers to the possibilities of evidence being contaminated by either contact with objects or people and how ‘every contact leaves a trace’ (Byard, 2016). There are certain processes in place from crime scene to court, such as the ways in which evidence is packaged, that exist to ensure continuity and these should be adhered to at all times to avoid any impact on the resulting findings. However, it is vital to recognise cases where contamination of evidence has in fact occurred, potentially leading to miscarriages of justice and whether or not it is realistic to assume that the risk of evidence contamination can be so easily removed by applying Locard’s exchange principle. At the centre of all forensic investigations is Locard’s exchange principle, a theoretical concept developed by Dr Edmond Locard to describe how evidence is transferred between objects. Locard’s exchange principle refers to how a perpetrator will bring outdoor physical matter to a crime scene as well as leave the crime scene with something from within. To simplify this concept and example is that a murderer will leave evidence at a scene as well as take evidence away with them, this could be as leaving a stray hair at the scene but also leaving with a hair from the victim on their clothing. Therefore, it is vital that all forensic practitioners work under the premise that they too will unintentionally bring physical matter to a crime scene that will cause confusion and contamination of evidence. In order to remove this risk of contamination, forensic teams are required to use and wear specific protective equipment and clothing to eliminate Locard’s exchange principle. The protective clothing worn is called barrier clothing and is designed to prevent contradicting or irrelevant evidence being transferred to a crime scene. The basic clothing is to be used only once and disposed of correctly. This generally consists of shoe covers, a disposable suit with a hood, a face mask and latex gloves which may need to be retained if required (Roberts 2012). In addition to the clothing itself, it must be put on in a specific order and disposed of in a way that follows protocol, such as changing gloves between artefacts and minimising the level of communication at a scene if not wearing a mask. Each of these items are designed and required in line with Locard’s exchange principle to eliminate the risk of contamination of evidence as much as humanly possible.

As previously stated, all forensic practitioners are assumed to be competent enough to fully apply Locard’s exchange principles to ensure that contamination never occurs at crime scenes or within laboratories. It has been suggested that there should be no issue of contamination if all practitioners adhere to the riles, protective clothing, evidence packaging and transportation and work in line with Locard’s exchange principles. However, there are several cases where Locard’s exchange principles have been disregarded, leading to the cross contamination and lack of validity in crucial, case building evidence. A high-profile case with unreliable evidence that crossed over several countries including the UK and the US in 2007 was the Amanda Knox case and the murder of Meredith Kercher (Hooper, 2011). It can be argued that Locard’s exchange principles were disregarded through forensic practitioners taking their own interpretation on how their protective clothing should be used, a claim that can be reinforced through CCTV footage of the crime scene investigation. There have been many examples within this case of essential protective clothing being used incorrectly, leading to any evidence potentially being compromised. CCTV footage shows prosecutor Giuliano Mignini and detective Monica Napoleoni wearing their shoe covers outside of the apartment, rendering them useless and counterproductive as anything that could contaminate the crime scene from the floor outdoors is still being brought in (Injustice Anywhere, 2009). In addition to this, Meredith Kerchers bra, one of the most vital pieces of evidence in this case, is shown being collected by Patrizia Stefanoni not wearing the mask that all forensics practitioners are required to wear over their faces – particularly when collecting evidence. The bra clasp itself was an incredibly important piece of evidence in the Knox case and following this footage it appeared that it may have been compromised in several ways. The first issue was that the bra was unaccounted for and ‘missing in action’ for 46 days in between being photographed and collected and was eventually collected almost 5 metres away from the position it had originally been photographed in. Upon testing, 3 DNA profiles were identified suggesting a clear indication of contamination, meaning that it was an incredibly unreliable form of evidence at this point (Injustice Anywhere, 2016). This was due to the crime scene being effectively ‘destroyed’, there being no accurate DNA mapping of the scene and little precaution taken to preserve each item and remove the risk of contamination. Another obvious issue was the manner in which it was collected, with little care of how protective clothing was worn, increasing the risk of contamination. It is important to question whether such crucial evidence was intentionally destroyed or if it was simply a case of incompetence and a need for immediate further training. The Amanda Knox case was a prime example of how it is possible for Locard’s exchange principles to be disregarded through incompetence, allowing for contamination of evidence to occur despite the assumption that all forensic practitioners should be

experienced and qualified enough to follow these crucial principles at all times but unfortunately, is not the only case where this type of negligence has occurred. To reiterate, forensic investigators are assumed to follow Locard’s exchange principles alongside their competence and qualifications to eliminate the risk of contamination. As seen in the Amanda Knox investigation, this is not always the case. However, the crime scene itself is not the only area where evidence can become contaminated, there are strict rules and regulations revolving around the packaging, storage and examination of evidence on route and within laboratories. For example, each item of evidence needs to be placed into the appropriate bag or storage device separately to anything else and labelled clearly. Different types of bags should be used for wet and dry evidence to prevent contamination. Following on from this concept, once at the laboratory there are several things that need to be considered. If wet evidence arrives that needs to be dried, it should be placed in a suitable drying room that can easily be decontaminated, these drying areas vary through high tech and low-tech methods depending on the resources available. In addition to this, if the correct resources are not immediately available, wet evidence should be kept in an impermeable, air tight container to prevent the destruction of evidence through bacterial growth (Ballou, 2013). These are just a few of the regulations alongside constant precaution from crime scene to court that must be followed to avoid cross contamination. It can easily be assumed that forensic practises can be trusted due to the amount of importance placed on them and how much can rely on the results of forensic analysis.it is vital that forensic practitioners follow Locard’s exchange principle not only at crime scenes but also in laboratories.

It is important to identify that contamination of evidence can occur in laboratories, such as in the case of Adam Scott. In October 2011, Adam Scott was charged with rape in Manchester, a city he claimed to have never even been to (Dodd, 2012). In ordinary situations, it would seem that a DNA match such as this would be a secure way of identifying the perpetrator of a crime. The difference in this case was that Adam Scott was not even a suspect for the crime until the evidence reached the laboratory. Alongside his claim to have never even been to the city in question, there were queries into the accuracy of the forensic results and whether he was truly guilty. The forensic analysis was handled by the Teddington laboratory, run by LGC forensics and the following investigation sparked controversy around the results of many other cases handled by the firm that provides a DNA analytical service to many police forces. In a report published by Andrew Rennison on behalf of the Forensic Science Regulator in 2012, it was found that Adam Scott was not in fact guilty of the offence but simply a victim of poor procedures and contamination of evidence. It was discovered and witnessed by other LGC forensics employees that the plastic trays to hold samples were being incorrectly reused. Although the sample taken was indeed a true match to Adam Scott,

it was not the same sample taken from the rape victim. The tray used for the sample from the rape victim had been reused, allowing for Scott’s saliva (from a sample that had previously been analysed) to be present and his DNA be incorrectly identified for a crime he did not commit (Rennison, 2012). The case of Adam Scott is a drastic example of how such a small mistake can have such a big impact. The rules of forensic practises exist in line with Locard’s exchange principle to eliminate the risk of contamination or miscarriages of justice, therefore it is vital that all forensic teams follow them at crime scenes and in laboratories. It is assumed that all forensic practitioners are competent with this yet the Adam Scott case reveals how simple but important mistakes can still be made and why it is so important to take every precaution when handling samples of evidence. One positive to take from both of these cases is that both Amanda Knox and Adam Scott were acquitted of their charges due to ‘stunning flaws’ in the Knox investigation (Kirchgaessner, 2015) and Scott due to proof of contamination within the laboratory. However, the worrying part of this is that had there been no further investigation into the forensic work done, both of these people would have been falsely charged and would continue to be incarcerated for crimes they did not commit. In contrast to cases where contamination of evidence has occurred through human fault and a lack of competence in Locard’s exchange principle, there are many ongoing studies and processes that exist to improve procedure to further reduce the risk of contamination of evidence. As DNA evidence plays such an important role in today’s criminal investigations, as well as technology advancing to be able to detect DNA from the smallest fragments of evidence, it is important for forensic teams to also develop their decontamination methods and use the most advanced precautionary techniques to counteract how easily contaminated areas can allow for incorrect DNA matches. Phantoms in the Mortuary – DNA Transfer During Autopsies is a report based on a study into the transfer of DNA from autopsy tables, instruments and bodies to discover whether the best cleaning products and processes were being used. The results from the investigation revealed that in 4 out of 6 cases, transfer of DNA from the autopsy table to a body was detected. This led to the experimentation with different cleaning products to decipher which would best remove this issue (Schwark, 2012). In the Adam Scott case, the issue was the reuse of trays in the laboratory which can easily be avoided. Laboratory tables on the other hand, are much less disposable and must be properly decontaminated in between subjects. The tests revealed that products containing bleach were the most effective. This type of study reveals how forensic practitioners are competent in applying Locard’s exchange principle to understand how easily contamination and DNA transfer can occur as technology develops. This is evidence of Locard’s exchange principle being applied to find the best method to eliminate contamination or transfer of evidence that could lead to miscarriages of

justice. Studies such as this lead to improving continuity and trust in forensic analysis as it emphasises how cautious most are despite the media making a point of harshly documenting when forensic practitioners make mistakes. This is an example of where forensic practitioners are competent in terms of qualifications and experience to fully apply Locard’s exchange principle to ensure contamination does not occur in laboratories. Therefore, there is no excuse for the contamination that occurred throughout the Amanda Knox and Adam Scott investigations.

Overall it is accepted within the criminal justice system that every forensic practitioner can competently apply Locard’s exchange principle to ensure contamination never occurs. However, there are several unfortunate cases where contamination has occurred and led to controversy, official complaints and miscarriages of justice. The Amanda Knox case is a serious example of forensic teams deliberately rejecting official procedures perhaps to save time or maybe even to deliberately alter findings. Either way, investigators took their own interpretation on how equipment should be used, cutting corners and negatively impacting a lengthy investigation. It appears the truth of the Amanda Knox case and the murder of Meredith Kercher will never fully be known due to the faults and lack of competence of the investigators. Rules and regulations exist to avoid this happening and the destruction of the crime scene through lack of competence and the issue of contamination should never have occurred practitioners had worked with Locard’s exchange principle in mind. The Adam Scott case on the other hand was due to a simple mistake in the laboratory which may be blamed on laziness or a lack of resources. Although a simple error, it caused a man’s life to be tainted by being wrongfully charged of rape- an offence that carries many judgements and potentially a reputation that lasts forever despite his later proven innocence. The reuse of forensic trays may be a simple error, but it led to contamination that also should not have occurred. The study into DNA transfer during autopsies was a great way to prove the competence of forensic practitioners to apply Locard’s exchange principle to decrease the risk of avoidable contamination as technology develops and more studies should be conducted across other areas to further eliminate the risk of contamination of evidence. In conclusion, it appears that forensic practitioners are generally competent and qualified to avoid cross contamination as Locard emphasises, with a few unfortunate exceptions that should never occur and should always be followed by further investigation and potential alterations to training as forensic technology becomes more advanced.

Ballou, S et al. (2013). Best Practices for Evidence Handlers. The Biological Evidence Preservation Handbook. 1 (3), p9-13.

Byard, R. (2016). Locard’s Principle of Exchange, Dental Examination and Fragments of Skin. Journal of Forensic Sciences. 61 (2), p1-3. Dodd, V. (2012). Forensics firm investigated over DNA blunder in rape case. Available: https://www.theguardian.com/law/2012/mar/09/forensics-firm-investigated-dna. Last accessed 6th Jan 2018. Hooper, J. (2011). Amanda Knox prosecution evidence unreliable, appeal court hears. Available: https://www.theguardian.com/world/2011/jun/29/amanda-knox-dnaevidence-contaminated. Last accessed 19th Dec 2017. Injustice Anywhere. (2009). CSI Contamination. Available: http://www.amandaknoxcase.com/csi-contamination/. Last accessed 19th Dec 2017. Injustice Anywhere. (2016). The Bra Clasp: Compromised Evidence.Available: http://www.amandaknoxcase.com/meredith-kercher-bra-clasp/. Last accessed 19th Dec 2017. Kirchgaessner, S. (2015). Amanda Knox acquitted because of 'stunning flaws' in investigation. Available: https://www.theguardian.com/us-news/2015/sep/07/amanda-knoxacquitted-because-of-stunning-flaws-in-investigation. Last accessed 6th Jan 2018. Rennison, A. (2012). Report into the circumstances of a complaint received from the Greater Manchester Police on 7 March 2012 regarding DNA evidence provided by LGC Forensics. Forensic Science Regulator, p2-15. Roberts, J (2012). Forensic Ecology Handbook. UK: John Wiley & Sons - Blackwell. p37-42. Schwark, T. (2012). Phantoms in the mortuary - DNA transfer during autopsies. Forensic science international. 1 (1), p10-40....