December 01 2022
Go into any second-hand clothing or furniture shop and you’ll see that ‘old fashioned’ has become ‘vintage’. And, as the average age of criminal law practitioners increases, there will be many, like us, who remember some ‘vintage’ forensic examinations the ‘first time around’. Our children roll their eyes and complain about how OLD we are, and we give a collective sigh and think ‘ah, the wisdom of youth…’.
Some branches of forensic science are the same now as they were many years ago. It may be that digital forensics and DNA are high fashion and some ‘vintage’ evidence types seemingly as unpopular as a pair of plus fours on the golf course, but that doesn’t mean they’re not still very useful in the right setting.
Disappearing without a trace
Traditional forensic disciplines involving footwear marks, glass fragments, textile fibres and paint flakes are relatively uncommon these days. If we go back 20 years or so, such trace evidence examination was among the ‘bread and butter’ work we reviewed or even carried out at Keith Borer Consultants. The Forensic Science Service routinely undertook background level studies of glass and fibres. The paint analysis section had access to a database of car make, model and year paint samples. It was commonplace to look for fibres on a seat taping to see if any matched the clothing of a suspected car thief, or to look at footwear marks at the scene of a burglary and establish the type of footwear the perpetrator might have been wearing.
These days, we are more likely to see a digital trail showing the suspect’s mobile phone was likely to be in the area at the time an assault took place, or a DNA profile from a discarded piece of clothing; not quite the ‘link’ to a scene or vehicle that matching clothing fibres or a footwear mark have provided in the past.
Why the change?
DNA solves many crimes with an accuracy that is hard to beat when the evidential circumstances are right. But the switch to DNA required a lot of space and a lot of scientists. During this shift, traditional areas of forensics appear to have been squeezed out. Tape-lifting loose surface debris, analysis of the tape-lifts, recovery of glass particles or individual fibres and comparison with samples taken from one or more reference samples (usually the suspect’s clothing or glass from a window) often requires many hours of work, some relatively expensive equipment and a good amount of bench space in which to work.
A report by HM Inspectorate of Constabulary and Fire & Rescue Services (HMICFRS) in August 2022 highlighted the need to go back to basics when conducting investigations. In relation to forensic evidence, they reported that in 71% of cases, victims of crime were not given any advice on crime scene preservation. The first thing I imagine most people would do is sweep up broken glass and give every surface a good wipe down, destroying much of the physical evidence we are talking about in this article!
Just because something is out of fashion doesn’t mean it isn’t fit for purpose. We have been instructed in cases involving physical fits, where broken parts, glass fragments or pieces of torn or cut cling film, duct tape or fabric are examined using microscopy and specialist lighting to see if they physically match to each other. A complex physical match is as good as any form of identification. This is relatively low-tech science but can provide crucial evidence in things like drugs supply cases, physical assaults or hit and run vehicle events. Physical fit is one of the few types of evidence where it can be certain that two or more items were from the same original object. Even DNA analysis doesn’t claim this.
We examined a large quantity of discarded packaging materials in a recent case and were asked to comment on the likely number of 0.5kg and 1kg drugs packages present. Our expert concluded that the total weight of Class A drugs involved was considerably lower than the prosecution’s estimate.
In an armed robbery case, several people broke into a shop and used hammers to break display cases. They stole items from the shop and made their escape by car, the vehicle being abandoned a very short time later. A pair of gloves believed to have been worn during the incident were found inside the abandoned car. The armed robbery was caught on CCTV and we were instructed to consider whether or not glass fragments would be found on the recovered gloves, had they been worn by one of the offenders.
The prosecution laboratory had examined the gloves and found a DNA profile matching one of the suspects, but no glass fragments. They concluded that there was no association between the gloves and the broken glass. Their view was the absence of glass was effectively neutral.
Our examination included a review of the CCTV evidence and, with our experience of how glass breaks and transfers to nearby surfaces, led us to the conclusion that the perpetrators should have been very heavily contaminated with glass fragments, including on any gloves they were wearing. The case was dropped.
Paint a picture
In a burglary case, the alleged offender (a painter) had legitimate access to the scene but not to a box containing valuables within it. Much was made of a ‘paint smear’ on the box but, before a full forensic examination could be carried out, the smear was compromised by fingerprint treatments undertaken on the box.
With the smear now bonded to the box, it could not be sampled and compared with paint being used in the house by the defendant. Little thought seems to have been applied to the overall forensic strategy in this case and, whilst the prosecution may well have lost some useful scientific evidence, more importantly the defence lost the ability to scientifically challenge the inferences being made in relation to the (chemically) unidentified smear on the box.
Leaving your mark
In times gone by, large numbers of footwear mark cases were submitted to forensic providers each year and, consequently, good background databases were built up in forensic laboratories and police footwear units, helping practitioners to see what patterns of footwear were common amongst people suspected of crime and which were more unusual. It also helped build up hard copies of footprints from submitted shoes which could be used to determine size and wear variations, a great help in interpretation. A slump in footwear mark cases now means that some collections are not very up to date regarding trends seen amongst suspects and a lack of hard copy examples also means that interpretation of evidential strength can be more intuitive than scientific.
In some footwear mark reports, we might see a comment to the effect that ‘the shoe could not have made the mark in its current condition’. In these cases, there will typically be some correspondence in pattern and size but the shoe, as seized, is too worn to have made the scene mark. The difficulty in interpreting these cases lies in being able to determine what is a reasonable wear difference to accept, given the type of footwear and the specific time lapse between offence and shoe seizure. Again, this is often quite intuitive, rather than demonstrably scientific, but, in the past, access to comprehensive footwear mark collections and sight of similar makes and model of shoe have really helped practitioners consider this complicated issue.
We do still encounter footwear mark cases where scientists have made errors in the initial examination. In one example, a Crime Scene Investigator had recorded a quite extensive footwear mark across two smaller adhesive lifts which had been butted together. Prosecution scientists received separate lifts and treated each individually, failing to notice that they were dealing with a single mark. When treated as two marks the experts could not exclude the suspect’s shoe as having made it but, fortunately, our expert noted (from ‘alignment’ marking on the back of the lifts) that it was actually a single mark and its overall size was different to the suspect’s shoe, allowing it to be excluded. This resulted in matters relating to this scene being dropped.
The future for trace evidence
HMICFRS has recommended that by March 2023 all police forces should ensure crime scene management practices meet professional practice guidelines for the investigation of burglary, robbery and theft. It will be interesting to see if this results in a renewed focus on the collection and analysis of physical evidence like footwear marks, glass and fibres. Sometimes, if you want information on who might have driven a car recently, the answer is better served with matching fibre evidence than trying to find DNA.
If the demand increases, then we anticipate more training for scientists will be needed, as a large proportion of those who had the skills and experience to analyse and interpret physical evidence cases have left the profession. Universities still teach the fundamentals of footwear, glass and fibre evidence and often include recovery and analysis of traces in practical exercises, but a basic understanding of the principles involved is not the same as many years’ hands-on experience where, for example, an understanding of regional differences in footwear choice or ‘fashion trends’ amongst the criminal fraternity are more apparent.
The next few years should show whether we see a return to these traditional forensic disciplines or whether they continue to dwindle.
Keith Borer Consultants can help
With our collective experience of almost 100 years in trace evidence examination, we are able to review evidence and comment on what other examinations could or should have been carried out to assist the case. Please contact the Durham office on 0191 332 4999 for assistance or email email@example.com.