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Fingerprinting – where chemistry and forensic science can come together

By William Peveler, on 26 May 2014

Researchers at Hanyang University in Seoul have recently published work in Nature Communications describing a new polymeric material they have developed, which is capable of mapping sweat pores in the human fingerprint at high resolution (doi). The polymer changes colour and becomes fluorescent when exposed to moisture (hydrochromic), even at low concentrations, and thus when a finger mark is deposited on a sample of the material, a point pattern fluorescent image is generated which can be recorded with fluorescent microscopy. The researchers go on to compare a selection of these to ninhydrin-stained latent marks, also exhibiting pore structure, to show a good match. They argue in their paper that the analysis of sweat pores in marks, rather than the typically used ridge structures, means that an incomplete or indistinct mark can still be used to generate a match if sweat pores are available. They neglect to discuss, however, the availability of sweat pore location information in lifted marks; and all their analysed marks were deposited directly onto the polymer itself or digitally scanned, rather than a more realistic examination of real world marks against their material as a reference.

It is exciting to see work with a strong forensic component featuring in such a high impact publication, beyond the normal forensic science journals, and this is partly due to the high quality chemistry content regarding the design and synthesis of their new polymeric material, and an in depth analysis of its hydrochromic properties. There is a good chance that this work will be widely covered in the popular-science and lay media too, due to the all-important CSI effect (e.g. here). However, are the results reported actually important forensically – or are they merely a handle to boost a good supramolecular chemistry paper to being a superstar nature paper? As the Korean authors admit, the materials they describe are not entirely novel; this class of polymers was first posited for mark development by an Australian group led by Tahtouh in 2011 (doi). However this initial research was published in Forensic Science International, where no doubt it escaped the notice of much of the chemical sciences and of the wider establishment, despite its forensic rigour in investigating the application of these polymers as mark developers on a variety of surfaces.

So maybe there are two messages that can be taken from this paper. Firstly, the mapping of sweat pores within finger marks may be an important part of dactyloscopy in the future, with the advent of new materials such as these allowing easy collection of sweat pore information.

However, a second message to take away might be that; if, as a forensic scientist you’ve stumbled across what you feel might be the next big thing, maybe get together with a chemist/physicist/etc. and big up the background science, and offer it to a journal beyond the forensic sphere. For example FSI has an impact factor of ~2.3 whereas Angewandte Chemie Int. Ed. scores ~13.7, and as evidenced by a recent spate of fingerprinting related papers they have published, the latter loves a good forensic science article. The chemists carrying out this fundamental research into novel development agents and materials often do not understand the intricacies and limitations of day-to-day practitioner case work, and the forensic scientists working on minor improvements to their well honed but basic techniques often do not look at the high-level theoretical work going on to further their ideas –it’s time to get the two together and then maybe there could be a lot more Nature papers on forensic science.

Many thanks to Helen Earwaker for informative discussion. Lee et al. 2014 “Hydrochromic conjugated polymers for human sweat pore mapping”. Nature Comms, 5, 3736 – is available as an open access paper from dx.doi.org/10.1038/ncomms4736.

CFS Seminar Series – Dave Baldwin PFS

By Michaela Regan, on 11 March 2014

March 6, 2014

This week’s seminar was a brief introduction to the use of tool mark comparisons in criminal investigations. It was given by Dave Baldwin who has experience working for the Forensic Science Service (FSS) and for Principal Forensic Services.

The seminar provided us with a brief background into the different types of tool mark impressions such as impressed marks (when a contact forces them together without movement) or dynamic marks (striations). These unique impressions allow an examiner to determine the action that caused the formation of such an imprint e.g. what type of instrument caused the forced entry to a door, the breaking open of a window, cut the fence or chain. Additionally, these marks can be left on the ribs or on the skull of a victim which allows the examiner to associate a suspect to a knife or weapon.

The complicated part is that it is important to understand the information surrounding the case as he needs to know what questions need to be answered in order to determine the right course of analysis. For example, are we trying to associate a suspect to a weapon or deduce whether that particular object caused the impression at the scene? Are we trying to determine the type of instrument that would have caused this impression like a screwdriver, and is it possible to determine that a specific object at a scene caused the impression?

The examiner will look at a variety of features to answer these questions such as:
- Class features: measurable features of a specimen which indicate a restricted group source
- Sub-class features: discernible surface features of an object which are more restrictive than class characteristics
- Individual characteristics: marks produced by the random imperfections or irregularities of tool surfaces. These random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion, or damage. They are unique to that tool and distinguish it from all other tools.
- Manufacturing processes: involves the transfer of rapidly changing or random marks on to work pieces caused by tool wear and chip formation or by electrical/chemical erosion. Microscopic marks on tools may then continue to change from further wear or abuse. These irregularities are considered unique and capable of being used to individualize or distinguish one tool from another.
- Finishing processes: sanding of lands resulting in unique land impressions to make it look attractive.

To analyse these features, examiners use a variety of instruments such as bench and comparison microscopes, casting techniques and a new instrument that is occasionally used is a comparison SEM (scanning electron microscope). This allows them to compare and contrast their analysis, but since these are compared they are at risk to a degree of subjectivity. Therefore, it is important to remain as objective as possible by following a rigid scientific methodology as bias is becoming an increasing issue within forensics analysis.

Finally, this introduction gave a small insight to the duty of a forensic tool mark examiner and the critical eye one needs to have to perform such work. Further, it showed the ease with which bias can cause the occurrence of inaccuracies in the analysis stage showing that great care needs to be taken when dealing with any type of evidence.

CFS Seminar Series – Julie Allard PFS

By Sally Gamble, on 27 February 2014

February 6, 2014

This seminar was from one of Principal Forensic Services’ forensic biologists, Julie Allard, who specialises in body fluids and their potential to provide DNA profiles for use in a criminal investigation. The types of body fluids discussed included blood, semen and saliva, all of which have presumptive tests for their detection:

  • Blood – Leucomalachite Green (LMG) test
  • Semen – Acid phosphatase test
  • Saliva – Phadebas test

These tests produce a colour change indicating the presence of the body fluid in question, and can be used on different materials including clothes and weapons. Once areas presumed to contain these body fluids have been identified, samples can be sent for DNA profiling. This is where it starts to get a bit tricky, not only can different levels of interpretation be addressed in relation to the DNA evidence obtained, the DNA evidence itself can be troublesome! For example, is there enough DNA present to produce a profile? Is there a mixture of two or more people’s DNA present? Has the DNA profile come from the body fluid in question? Whose DNA and therefore body fluid is present in the sample? Can the presence of a given person’s DNA determine the actions of that individual?

Julie emphasised the importance to take the context of the case into account when answering these questions. A forensic scientist may address the activity level of the evidence, e.g. Person A kicked Person B but must not address the question of whether or not a person committed a crime or not, since this is the job of the jury. The CAI (case assessment and interpretation) model aids a forensic scientist in evaluating the evidence they are given in a balanced, logical, robust and transparent manner.

However, the interpretation of evidence for use in court is a contentious subject, Julie pointed out that as new information arises concerning a case, the evidence must be re-evaluated in light of this new information. Furthermore, it is likely that the information that the prosecution scientist has received does not correlate with the information received by the defence scientist, leading to much disagreement between experts!

Finally, for forensic scientists to effectively use the CAI model to clearly show how a given conclusion was derived from the evidence provided, in light of the case information, Julie stressed that the logical assessment and interpretation steps need to be based upon empirical data that mimics the forensic context.

www.principalforensicservices.com

CFS Team at AAFS

By Aysha Chaudhary, on 18 February 2014

The annual meeting of the American Academy of Forensic Sciences is currently underway in Seattle. Dr Morgan will be in attendance, accompanied by a group of CFS doctoral students who will be presenting their research.

Helen Earwaker will be presenting her poster titled “Fingermark Submission Decision Making Within a United Kingdom Fingerprint Laboratory: Do Experts Get What They Need?”
Criminalistics Poster Session [Wednesday]

Georgia McCulloch’s presentation is entitled “Is High Performance Liquid Chromatography (HPLC) a Useful Addition to Current Geo-Forensic Analytical Techniques?”
Criminalistics Session II [Thursday 1:30pm]

Michaela Regan will be presenting her poster, titled “A Study to Determine the Use of Gunshot Residue Upon Clothing as an Item of Evidence”
General Poster Session [Wednesday]

Sherry Nakhaeizadeh will be giving a presentation on “Cognitive Bias in Forensic Anthropology: Visual Assessments of Skeletal Remains Are Susceptible to Confirmation Bias”
Physical Anthropology [Friday 12:00pm]

Dagmar Heinrich’s presentation is entitled “A “Realistic” Study of Sharp Force Trauma Recognition in Burned Remains: The Forensic Implications”
Physical Anthropology [Saturday 12:15]

CFS Seminar Series – Brian Rankin

By Nadine Smit, on 23 January 2014

CFS Seminar lead by Brian Rankin (Head of the Centre for Forensic Investigation, Teesside University)
January 22, 2014

In addition to most of the other seminars that focus on specific forensic studies, this seminar was aimed at highlighting the market issues around forensic science. If you were not aware of the importance of this as a forensic science student or researcher, you would have been afterwards. Brian Rankin pointed out the main challenges, which were then discussed among the group. This forced you to think about the implications of these issues for the future of forensic science and yourself herein. I found it very enlightening to discuss these issues with someone that has experience in both the academic and policing environment, and who is very passionate and enthusiastic about his, and our, field.

For example, I think many forensic science students do not realise the importance of effective case management to save time and costs in the CJS, which is said to be improved by using streamlined forensic reporting. What also I found noteworthy and worrying are the different requirements for the laboratories in the police forces and the independent forensic companies to be accredited. To me, this also implies that the shutdown of the Forensic Science Service (FSS) resulted in many problems regarding quality assurance and maintaining the code of practice. Luckily, with the help of the Forensic Science Regulator, such issues are currently being addressed. Also, with the shutdown of the FSS, universities in the UK now bear the responsibility of research and development, which I believe should be done with close communication and participation of the government, police and commercial companies to guide forensic research to address current issues.

Examples were given, such as the investigative process of the murder on Jill Dando and the arrest of Shirly McKie which put some of the current issues into perspective. These are just two of many more examples that show the significant impact of the improper handling of forensic evidence. This seminar once again highlighted the importance of multidisciplinary and collaborative research in the forensic domain which was both eye-opening and encouraging. Lastly, even though job opportunities in this field are limited, it was highlighted that forensic science students are equipped with many skills that can be applied in a lot of other problem-solving environments.

CFS Seminar Series – Professor Bjorn Reif

By Aysha Chaudhary, on 18 January 2014

Professor Reif from the Norwegian Defence Establishment (FFI) gave an exciting talk on the use of computer models in understanding the distribution of explosive residue after an explosion had occured. The fundamental physics governing the movement of particles in air was outlined and a description of the computational fluid dynamics methods used to model the phenomenon was provided. Models produced at the FFI of the Oslo bombings were presented to demonstrate the accuracy of the method and the usefulness of combining computational skills with experimental data. The importance of understanding the dispersal and deposition of particulate explosive residues following detonation would not only be useful for forensic scientists looking to efficiently process a post-explosion crime scene and sample for such traces, but would also benefit subsequent environmental clean up procedures - in particular where ‘dirty’ bombs may have be used.

- Nadia Abdul-Karim