Prior to its closure in March 2012, the Forensic Science Service (FSS) had nearly 70 qualified experts in the area of footwear mark comparisons. FSS scientists undertook extensive training and mentoring to do this type of work and their findings were quality checked by another expert prior to a report or statement being issued. Footwear evidence is now produced by private forensic science providers and by in-house units in police forces. The number of people providing the prosecution with information or 'evidence' in this area is now much higher and their level of training, experience and expertise appears much more thinly spread.
The changing role of police footwear units
Many police forces initially set up footwear units purely to provide basic intelligence to investigators and to screen out ineffective submissions to forensic science providers. This work was traditionally carried out in-force by staff without specialist knowledge. Some forces have extended this role to the provision of 'evidential' statements, but not publicised the fact that the staff doing it may not be true experts in this field. The police staff employed to undertake these roles receive training from various sources, however, almost without exception, the training is not to the same 'expert' level as that required by staff working within the major forensic science providers. Some of these individuals now give evidence in court.
The National Policing Improvement Agency (NPIA) has taken the lead on providing training for police staff in this area, but much of this training has not been delivered by recognised experts in the field and trainees may feel that they return, virtually unsupported, to isolated units after having only a few weeks of training. With the demise of the FSS and the changing forensic market, some acknowledged footwear experts have migrated into various police forces. Many feel relatively isolated or are operating in roles with far more responsibility than they formerly had or were trained for. Some forces also do not have sufficient 'experts' for the 'evidence' they produce to be independently checked. Whilst having an in-force footwear examination capability saves time and makes intelligence much speedier, it also appears to save a force a considerable amount of money.
Keith Borer Consultants is increasingly encountering prosecution statements from individuals who are clearly not experts in this area of forensic science and we have found a number of cases where the prosecution footwear evidence has been inaccurate or unreliable when checked. Some of these deficiencies have been brought to the attention of the Forensic Regulator.
Footwear examination – the comparison stage
Footwear examinations involve two clear stages, first the comparison of the scene marks and the footwear and, secondly, the estimation of the evidential value of the correspondence found between them (i.e. the interpretation of the evidence). Keith Borer Consultants has encountered problems with comparisons, such as poor or no photography of the scene marks, poor comparison techniques and lack of contemporaneous notes.
Footwear examination – the interpretation stage
Having carried out a comparison, a competent footwear scientist should be able to explain why they think the correspondence is significant and to justify the strength of opinion they have assigned to the evidence. They should be able to describe the effects of pattern variation and frequencies, size and wear variation and the significance of the correspondence in damage features and explain how this helps to discriminate footwear of different pattern types and within a pattern type.
The NPIA maintains the National Footwear Reference Collection (NFRC) and provides the police and some forensic providers with electronic access to this. Police forces often have very extensive local collections of footwear impressions they have taken from suspects in custody. This type of information gives an indication of the relative frequency with which a particular pattern of shoe occurs within people suspected of involvement in crime within a particular area. This data has its limitations and needs to be used sensibly, for example pattern frequency of shoes from people suspected of burglary may have little relevance in a rape case, nevertheless the evaluation of such data forms part of the interpretation process.
Similarly, by reference to hard copies (i.e. test impressions) of a range of different sizes and states of wear for a particular pattern, a scientist can see, for example, how a size 7 is different to a size 8 over the area of the crime scene mark, or how the shaped blocks on a shoe sole change with wear. By using all of this information, a good scientist can tell if a pattern is unusual, if only a small size range of shoe could have made the scene mark, and if the wear correspondence is highly distinctive or common to most shoes of a particular pattern. Worryingly, KBC has encountered problems with the evaluation of evidence and, in some cases, there is little evidence of any interpretation as such, merely a statement of an evidential strength in the case notes with no explanation as to how it has been reached.
In our experience only around 10% of footwear comparisons provide conclusive evidence that a particular shoe made a particular scene mark. So for 90% of cases, the level of evidence obtained is only supportive. There is no universally accepted method or formula to determine the evidential strength of the observed footwear mark correspondence. The evidential significance depends on the degree of discrimination you are likely to obtain over the area of a scene mark in terms of pattern, size and wear. For some marks/patterns, the discrimination is high and the evidential significance great, for others it is low and the likelihood of a coincidental match much greater.
Court of Appeal – impact on interpretation
Following the landmark judgement in the case of R v T ( EWCA Crim 2439) in October 2010, many footwear examiners now state that they carry out their interpretations on the basis of their 'experience and expertise'. In truth, some people have very little of either, but this is not often apparent from the various types of reports/statements produced. As footwear mark comparisons can be done to many levels/standards, it is vital to ensure that the true value of the 'evidence' is established.
Points of note
Many people can do a reasonable comparison of the crime scene marks and the suspect’s footwear, given a degree of training, but assigning any evidential strength to the observed correspondence and being able to explain and justify it is a very different matter.
Asking some simple questions about a person’s training and their true level of experience and expertise can be very illuminating. Even accepting that your client’s footwear corresponds to a degree with a crime scene mark, what you really need to know, in some detail, is whether the same mark could have been made by another pattern of shoe, or could have been made by a shoe two sizes larger or smaller than your clients shoe, or whether a significant percentage of shoes of this pattern type would have more or less the same appearance in terms of wear, as your client’s. With answers to these questions, one can then move onto the rather arguable issue of the evidential strength.
Alan Henderson, Forensic Scientist