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How Effective is Forensic Science in Aid of Crime Scene Investigation

Literature review

The primary crime scene is the physical place where the crime has occurred originally and as such crime scenes may differ from crime to crime and a secondary crime scene is the physical place where some other evidence related to the crime is uncovered (Mooney, 2014). Forensic entomologists, pathologists and anthropologists have their specific areas of expertise that may be called upon to aid in crime scene investigation (Mooney, 2014). The task of the forensic experts is an essential part of the investigation into the crime, as well as the prosecution process. Thus, forensic science and the criminal justice process are closely aligned in the common objective of linking the offence to the offender. Recent miscarriage of justice cases have revealed that forensic science is not always successful in correctly linking the crime to the criminal.

The failure to achieve a desired end of justice is a miscarriage of justice where failure is accompanied by a breach of defendant’ rights (Walker, 2004, p. 32). The particular breaches of interests of defendants occur due to the use of deficient processes, laws; absence of factual justification for the treatment or punishment; disproportionate treatment of suspects or convicts vis a vis people whose rights need to be protected; efficient protection of rights of people, state law (Walker, 2004, pp. 32-33). Here forensic sciences play a very important role in helping the criminal justice system to achieve the desired result.

Evidence that can be used in criminal justice process may include: testimonial evidence, which is the testimony of the witnesses or the victim; physical evidence, which includes, fingerprints, documents, shell casings, etc.; biological evidence, which includes blood, saliva, hair, etc.; and trace evidence, which includes, fibres, skin cells and hair strands and it is important to note that biological and trace evidence may overlap at times (Mooney, 2014, p. 9). Evidence that links a person to the scene of the crime is also called as associative evidence and this may include blood, DNA, trace evidence, etc. (Mooney, 2014, p. 9). In general, of all the forensic evidence, physical and biological evidence is considered to be the most reliable and creates strong links between the person and the crime (Mooney, 2014, p. 9).


DNA evidence is now a well-known and highly regarded technique of forensic science. However, DNA, although scientific, has also led to some wrongful convictions. As some of cases regarding wrongful convictions show, the fault may not always lie in the science, but in the persons who are engaged with it or the faults may lie within the system (Gill, 2014). The fact is that DNA evidence can be contaminated. In general, the Locard’s Exchange Principle informs that each person entering the crime scene is capable of taking away or leaving his trace evidence (Tilstone, et al., 2006, p. 15). Locard has also said that it is highly probable that a perpetrator will leave some evidence of his link to the crime (Tilstone, et al., 2006, p. 15). However, the possibility of transfer or contamination of DNA evidence cannot be ignored.

In the Adam Scott case, the accused was identified as the offender on the basis of DNA evidence. The DNA was collected from Adam Scott in an earlier unrelated crime and as the events later showed, there was a contamination incident in the laboratory, which led to the mistaken analysis and results that tied up Adam Scott with the crime of rape. Not only that there was an incorrect assessment of the source of body fluid, which originally was DNA from saliva but was identified as semen (Gill, 2014). In Adam Scott’s case, the mistake was discovered early on and he was released. However, there have been cases from around the world that have seen innocent people convicted and incinerated for lengthy periods.

In Adam Scott’s case DNA collected in an earlier unrelated crime and its contamination led to his being accused in a crime. In an Australian case, R v Jama, similar facts were observed where DNA was collected in an earlier unrelated crime and then the contamination of DNA in a subsequent crime led to the prosecution (Gill, 2014). Interestingly, Jama’s DNA was collected in a rape case where his sample did not match and then the same sample was contaminated in another rape case one day after and was found to be a match (Gill, 2014). Jama denied any knowledge of the crime and said that he was not even in the area where the crime had been committed. Because the victim was in an inebriated state, the DNA evidence was the only link that the investigation had to Jama. The laboratory analysts, prosecutors, investigating agency, all were very confident that there could be no contamination of the DNA samples and Jama was convicted. However, later contamination was proved although the route of contamination of DNA sample could not be determined, leading to the quashing of the conviction (Gill, 2014).

The case of Birmingham Six or the Birmingham pub bombing of 21st November 1974, killed 28 people and injured more than 180 (Mullin, 1997). Omagh bombing of 15th August 1998, killed 29 people and left almost 300 people injured (Chalk, 2013, p. 185). The principal forensic techniques applied in Birmingham Six case were Griess test, Dr Skuse’s test, TLC and ‘sniffer test’. It is interesting that the Griess Test was widely disregarded as unreliable by the majority of forensic experts who testified in the case (Gudjonsson, 2003, p. 453). The creator of the TLC, John Yallop, testified in the court, that only the TLC test could not be relied upon for proving that nitroglycerine traces were found on principal accused, which were the members of the Maguire family (Gudjonsson, 2003, p. 453). Ultimately, the men were convicted on the basis of the Dr Skuse’s forensic test and the confessions obtained by the police (Gudjonsson, 2003). As it happened the six men’s convictions were later found to be incorrect. In 1991, the Court of Appeal quashed the convictions. As one writers puts it, “The Birmingham Six case also highlights the risk inherent in overestimating the role of the forensic science in criminal cases” (Knoops, 2013, p. 81).

For the Omagh bombing case, the forensic technique relied upon was LCN (Low Copy Number) DNA test. The entire case against the principal accused, Sean Hoey, hinged on the evidence obtained through LCN (Krimsky & Simoncelli, 2013, p. 176). There was some divergence amongst the experts on the use of the technique (Krimsky & Simoncelli, 2013). Ultimately, the test was able to convince the jury of the guilt of the principal accused. In both cases, the techniques proved inadequate or ineffective in coming to the desired outcome of fixing liability on the culprits.

In a case before the US Supreme Court, the court held that forensic evidence is not uniquely immune from the risk of manipulation…because the forensic scientists often are driven by the need to expediently answer a particular question in the investigation sometimes by sacrificing an appropriate methodology for the sake of expediency (Melendez-Diaz v Massachussets, 557 U.S. 305, 2009). This demonstrates the administrative realities of agencies or individuals involved in the forensic science process of criminal investigations and this can be one of the factors that compromises the efficacy of forensic science within the criminal justice system. It is difficult to have a central governing mechanism for forensic sciences as these are often fragmented into different categories such as, fingerprints comparison, handwriting identification, firearms, pathology, and fibre comparison (Roach, 2009). This ‘jurisdictional fragmentation’ means that forensics are not subject to common forms of governance and this presents problems in effecting reforms in the forensic sciences (Roach, 2009).

The reality of forensic science involves forensic scientists working through lengthy and tedious processes of examining, testing and interpreting evidence. The forensic scientists may face impediments in their task due to budget constraints, lack of training and lack of resources (Turvey & Cooley, 2014). Added to that, there is a requirement of forensic scientists to give their testimony in order to convince the jury of the link between the crime and the accused. Here, the complications within the adversarial criminal justice system and the lack of understanding of the same, may also prove to be a factor in not achieving the desired result (Sallavaci, 2014). Two cases within the English law relating to prosecutor’s fallacy may prove this point. In a case decided by the Court of Appeal, the court held that scientists should be mindful of investigative expectation and that they should not “fall into the trap of prosecutor’s fallacy, namely confusing the match probability that an innocent person would match the NCA sample from the crime scene, a matter on which they are entitled to act as experts, with the likelihood ratio, which is the probability that the matching individual before the court is innocent, a matter for the jury” (R v Deen, (1994) CA, 1994). This is also the first case in England and Wales where the prosecutor’s fallacy was identified.

In Deen’s case, the main evidence that linked him to the three rape cases, for which he was convicted and sentenced to 16 years of imprisonment, was DNA profiling (Sallavaci, 2014, p. 117). The fallacy that was referred to in the case was the confusion between match probability and likelihood ratio. The same question and problem of prosecutor’s fallacy was raised in Doheny v Adams, which is considered to be the most important DNA case in English law (Sallavaci, 2014, p. 118). In this case, the Court of Appeal clarified that scientists can only testify as to the match probability and not the likelihood, which is a legal matter and one that can only be decided by the jury. This brings one to another important aspect of forensic science, that is, the results of the forensic investigation have to be convincing enough for the jury to convict someone on the basis of such forensic science. Thus, forensic science by itself is not considered to be exact enough to point to the likelihood that someone committed an offence, which is a legal matter. In other words, forensic science is admittedly not exact and perfect although the forensic scientists may themselves consider that the results derived by them are infallible because they are scientific (Freckleton, 2000).

An oft neglected cause of the fallibility of forensic science’s effectiveness may also be the fact that forensic science results have generally been treated as incapable of fallacy and often forensic scientists may be in error when they treat their results as incapable of being incorrect because these are scientifically derived (Turvey & Cooley, 2014, p. 176). However, there is no such thing as absolute scientific certainty (Botkin, 2011). In forensic science, there is always a possibility of error as forensic science is not a perfect science. Ian Freckleton, an Australian forensic scientist has also cautioned forensic scientists in treating their results as the absolute certainty (Freckleton, 2000). He specifically mentions US, Australia and the UK with reference to miscarriage of justice cases, that show that forensic science is not always effective in producing the desired result. Such miscarriages of justice may occur due to flawed forensic science. An important point made by him was, “expectation can lead to self-deception and self-deception to the potential to believe to readily, to be deceived” (Freckleton, 2000, p. 326).

Literature shows that there are many cases in England and Wales that show the association between forensic science and miscarriage of justice. These cases are related to the effectiveness (or the lack of it) of forensic techniques in crime scene investigation.


    1. Botkin, D., 2011. Absolute Certainty Is Not Scientific. [Online]
    2. https://www.wsj.com/articles/SB10001424052970204630904577058111041127168 [Accessed 5 February 2017].
    3. https://www.wsj.com/articles/SB10001424052970204630904577058111041127168 [Accessed 5 February 2017].
    4. Chalk, P., 2013. Encyclopedia of Terrorism, Volume 1. Santa Barbara: ABC-CLIO.
    5. Freckleton, I., 2000. A Taxonomy of Error and Deviance. In: J. Nijboer & W. Sprangers, eds.
    6. Harmonisation in Forensic Expertise. Leiden: Thela Thesis.
    7. Gill, P., 2014. Misleading DNA Evidence: Reasons for Miscarriages of Justice. London: Elsevier .
    8. Gudjonsson, G. H., 2003. The Psychology of Interrogations and Confessions: A Handbook. Sussex: John Wiley and Sons.
    9. Katz, H., 2011. Justice Miscarried: Inside Wrongful Convictions in Canada. Toronto: Dundurn. Melendez-Diaz v Massachussets, 557 U.S. 305 (2009).
    10. Knoops, G.-J., 2013. Redressing Miscarriages of Justice: Practice and Procedure in (International Criminal Cases: 2nd Revised Edition). Koniklichke: Martinus Nijhoff Publishers.
    11. Krimsky, S. & Simoncelli, T., 2013. Genetic Justice: DNA Data Banks, Criminal Investigations, and Civil Liberties. New York: Colombia University Press.
    12. Mooney, C., 2014. Forensics: Uncover the Science and Technology of Crime Scene Investigation. Chicago: Nomad Press.
    13. Mullin, C., 1997. Error of Judgement: The Truth about the Birmingham Bombings. s.l.:Poolbeg Press.
    14. Roach, K., 2009. Forensic Science And Miscarriages Of Justice: Some Lessons From Comparative Experience. Jurimetrics, 50(1), pp. 67-92 .
    15. R v Deen, (1994) CA (1994).
    16. Sallavaci, O., 2014. The Impact of Scientific Evidence on the Criminal Trial: The Case of DNA Evidence. Oxon: Routledge.
    17. Tilstone, W. J., Savage, K. A. & Clark, L. A., 2006. Forensic Science: An Encyclopedia of History, Methods, and Techniques. California: ABC-CLIO.
    18. Turvey, B. E. & Cooley, C. M., 2014. Miscarriages of Justice: Actual Innocence, Forensic Evidence, and the Law. Oxford: Academic Press.
    19. Turvey, B. E. & Cooley, C. M., 2014. Miscarriages of Justice: Actual Innocence, Forensic Evidence, and the Law. Oxford: Academic Press.
    20. Walker, C., 2004. Miscarriages of justice in principle and practice. In: C. Walker & K. Starmer, eds. Miscarriages of justice: A review of justice in error. Oxford : Oxford University Press.

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