“… the Crown no longer opposes the appellant’s [additional DNA] ground of appeal, namely that the DNA evidence presented at trial was flawed. … it is the Crown’s position that the flaws in the DNA evidence render the appellant’s conviction unsafe.”
“(c) Mixed profiles and partial profiles 15. The procedure as we have described it assumes that a full profile can be obtained of the DNA recovered from the scene of the crime or other relevant location and that the sample contains the DNA of only one person. However, in practice samples often contain the DNA of more than one person, in which case the analysis will produce what is known as a ‘mixed profile’. A mixed profile can be identified by the presence of more than two alleles at any single locus. In such cases it is necessary to identify the number of contributors to the profile and to establish separate profiles for each of them. This gives rise to certain difficulties in the interpretation of the results of the analysis to which we shall return. Moreover, even in a case where there is only one contributor to the sample, it may not be possible to obtain a complete profile, that is, to identify two alleles at each of the 10 loci. A profile in which, for whatever reason, some alleles cannot be identified is referred to as a ‘partial profile’. 16. In a mixed sample originating from two or more persons it is often the case that one person (the ‘major contributor’) will have contributed much more of the DNA present than the others (the ‘minor contributors’). That results in higher peaks appearing on the graph at the locations of the major contributor's alleles and lower peaks appearing at the locations Page 9 of alleles obtained from the minor contributors. Where the major contributor and a minor contributor have the same allele at the same location the peak produced by the minor contributor's allele will be hidden by that produced by the major contributor's allele. This phenomenon is known as ‘masking’ and may account for the apparent absence of an allele belonging to the minor contributor. The presence of a stutter in the profile of the major contributor may also mask an allele in the profile of the minor contributor. 17. If only a partial profile can be obtained from the sample under test there will be some loci at which only one allele, or perhaps no alleles at all, have been found. That may be due to a variety of causes which include masking, the loss of some molecules from the sample and the tendency of molecules with a high molecular weight to degrade. In very rare cases there may be no allele at that locus. Such ‘voids’ are potentially significant because, if the missing allele did not match either of the alleles at that locus of the person under investigation, it would establish conclusively that he (or she) had not provided that sample of DNA. Every partial profile carries within it, therefore, the possibility that the missing information excludes the person under investigation, but there is currently no means of calculating the statistical chances of that being the case.”
“Unless there is a reasonable expectation of sample(s) originating from a common source (eg duplicate vaginal swabs or a bone), allelic data from separate extractions from different locations on a given evidentiary item should not be combined into a composite profile.”
“Replication should be applied whenever a poor quality profile is to be relied on to progress an investigation or provide evidence against a suspect. It assists in evaluating reproducibility, identifying spurious peaks and informing conclusions relating to the likelihood of allelic drop-out and the number of contributors. Replication allows a fuller understanding of the nature of the sample and reduces the scope for conjecture and the risk of misinterpretation...”
“Test results at loci should either be interpretable or not interpretable and that determination should be made in the absence of any information about persons of interest in an investigation. The reporting of more than one statistical weight for a single evidence sample is a clear sign that a testing laboratory has applied an inappropriate, suspect-centric approach to its generation of a combined probability of inclusion/exclusion statistic.”
“The possibility of allelic drop out at many or all of the loci used to calculate the CPI significantly underestimates the chances of a random individual failing to be excluded as a contributor to that sample.”
“In conclusion, there were significant errors in [the] way in which statistical weights were attached to the failure to exclude persons of interest to evidence samples in Julian Washington’s 2014 trial. Some of those errors should have been known at the time the testing was performed and others have come to be more broadly understood in the years since the analyses were performed. It would have been most appropriate to have characterized the testing of the casings sample in Mr Washington’s case as ‘inconclusive’. Instead, jurors were given an unreliable statistical weight of ‘one in 46 million’ and where the statistic was inappropriately represented as being equivalent to a chance of innocence in a clear example of what has been known since 1987 as ‘the prosecutor’s fallacy’.”
“‘3.4.3.1. If composite profiles (ie generated by combining typing results obtained from multiple amplifications and/or injections) are used, the laboratory should establish guidelines for the generation of the composite result’. (Dr Llewellyn’s emphasis). The laboratory did not demonstrate that they had the validation studies or procedure guidelines to support their ability to create a composite DNA profile for sample JAH 1-3, 5 using 5 different electropherograms from 5 different analysis. [sic] Therefore, the use of this composite DNA profile does not meet the 2010 SWGDAM Interpretation Guidelines for Autosomal STR Typing by Forensic DNA Testing Laboratories and should not be used for inclusion.”
“… she is saying the possibility that this profile, in which she said [the appellant] was included, was related to someone other than [the appellant] was one in those millions. The odds that it belonged to somebody else, then, other than [the appellant] was one in 46 million when you consider the Bermuda Black Population ….”