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Ask Laura

Please post your questions for this week in the comments section. Laura will select the most liked/interesting questions and publish her response to these on this step by Wednesday of Week 6.

Thank you very much for all your excellent questions and comments again this week, I hope you are enjoying the final week of the course, bringing together all of the scientific evidence we have looked at as the case has unfolded. This week, your questions were almost all about the case itself, so I’m going to focus on this in my answers. In previous weeks I have tried to answer questions that are less directly related to the case so that your knowledge and understanding of the case develops alongside the evidence being presented to you, but since we are now nearing the end of the course I will try to clear up some of your issues with the case. Hopefully any remaining questions you have will be cleared up in the final big reveal of the verdict on Friday…

Firstly, throughout the whole course, a lot of people have asked about gunshot residue (GSR) and whether any test for this could have be done in this case. Amanda Wilbur, Ruby Corbett, Caroline Bowyer, Lynnette Davidson and Maureen R all asked about the analysis and persistence of gunshot residue and in some case contexts this could give you some useful information. However, there are some important limitations of gunshot residue evidence, particularly in this specific case. The first is that in any shooting, particles of gunshot residue are transferred onto surfaces near to where the gun was fired, including skin, clothing, nearby surfaces etc. as it can travel approximately 1 metre to the side and 3 metres forward, however they are also lost very easily. Many forensic laboratories will not accept items for examination for gunshot residue if they are collected more than a few hours after the incident took place, as it would be unlikely to produce any useful information. Simple washing can remove GSR from hands and regular wear can remove it from external surfaces of clothing. The second limitation, specific to this case, is that here we have a situation where two people were shot inside/around a vehicle i.e. in a confined space, and so it is likely that there will be a lot of gunshot residue all over those people and the inside of the car. Mr Ward’s hands could be tested for gunshot residue, but if this is found then it could be explained by him touching his own arm where he was shot, touching Mrs Ward or touching the inside of the car. So whilst it might be possible to identify gunshot residue, we have to think about the distribution and whether or not this would actually be useful investigative information.

Related to this, a few people this week asked about whether any other useful evidence was recovered from the gun. Nola Bogie and Maria Hoy asked whether any fingermarks were found on the gun, and in previous weeks there have been several questions about whether any fingermarks or DNA could be recovered from the gun after it had been in water, and generally whether any other useful evidence was found on the gun. The answer in this specific case is no, there wasn’t anything else useful found on the gun. In general, it is not possible to answer definitively the question of whether it is likely there would be any useful evidence remaining on the gun after it had been in water. A gun may have been cleaned, or the person who used it may have worn gloves, so there may not have been any useful evidence on the gun before it went into the water. If there was fingermark and DNA evidence on the gun then this would have started to degrade once it went into the water, and this would be more likely to occur if there was motion of any sort, such as tides or winds moving the water around. Many components of fingermarks such as sweat are water soluble, as is DNA, and so these would eventually be washed away. The length of time it would take for this to happen would depend on many factors, including the length of time the gun was in the water, the type of water (e.g. freshwater or saltwater), and the amount of the material that was transferred in the first place.

The questions relating to the analysis of illicit substances covered a few different areas, and there were questions and comments from Sugam Shrestha, Carol Wilson and Eric Ezequiel Acevedo about the use of presumptive and confirmatory tests and cutting agents.

On the topic of presumptive testing for drugs, for all of these tests, there are a variety of substances that can cause false positive results on the tests, which means that the results of these tests cannot be used to definitely conclude that a substance is present. As such, a presumptive test cannot be reported formally, and a forensic scientist would not testify in court about the results of such a test. False positive results on presumptive tests for drugs have been reported, as a result of cross-reaction with drugs that are not illegal, including some prescription/pharmaceutical drugs, such as aspirin. In addition, some everyday substances give false positive results on these tests, for example Pritt stick glue gives a false positive on a test for cocaine, and nutmeg and thyme give false positive results on a cannabis test. The issue with this potential for false positive results means that presumptive tests cannot be relied upon, and more detailed confirmatory analysis needs to be carried out before a forensic scientist can conclude that a substance is present. The only time that a presumptive test result would be presented in court would be if the accused individual has admitted to possession of the drug tested for, and then this test would be admissible. In all other cases, a confirmatory test would be required, and this would usually be a GC-MS test. This relates to the question about TLC and GC-MS and why both tests are done. Whatever presumptive test is carried out is useful for indicating what substance may be present, and this also helps the drugs analyst to determine exactly how the confirmatory test will be done, so the TLC result can give an indication of what should be done as a follow up. The presumptive test is cheap, quick and simple and prevents the lab from having to use up more resources testing for different drug types using the confirmatory technique. However, if the lab had a trace drugs case, where there was only a very small amount of the drug, then they might well skip the presumptive test step and go straight to a confirmatory test. One final comment about false positives is in fact that often the colour seen is different to that expected and so this can be indicative of a false reaction.

Harry Price asked about the accuracy of blood spatter analysis (BPA). BPA is a fascinating area of forensic science grounded in Physics but it is still incredibly subjective. In some circumstances where it has been a dynamic event with lots of movement it is possible to determine the sequence of events from the BPA and even what has happened where, however, whilst it is possible to use BPA to determine a vicinity it is impossible to pin point an exact location. Similar to the GSR answer above, as this particular offence occurred in the confines of a car, BPA is likely to be of limited evidential value due to the close proximity of everyone involved.

Finally, Ian Horne asked about the current state of Forensic Science in the UK and the role of the Forensic Regulator, I cannot comment for my colleagues but in my personal opinion I do agree that the forensic regulator should be given statutory powers to enforce standards, quality and accreditation across all disciplines of forensic science and in all providers, whether the private commercial sector (who already adhere to these standards and pave the way for quality), smaller defence contractors or the Police. It is also my personal opinion that state run provision is not possible nor necessary in the UK, but that certainly something needs to be done to stabilise and regulate the market – an area that I am currently conducting research in to.

All that remains now is to say that I hope you enjoy the rest of the material in Week 6. The video revealing what really happened will be made available at 16:15 GMT this Friday, 8th November, and we are asking you to vote up to 16:00 BST on Friday for whether you think Mr Ward is guilty or not guilty. We really hope you will take the time to vote, and we would love to see lots of responses. I would also encourage you to vote according to your analysis of the evidence, and not on your gut feeling. This week we have been looking at a logical system for bringing together evidence and analysing it and thinking carefully about what it means from a scientific point of view. You should therefore focus on the science, work through it all logically and base your decision solely on what the evidence tells you.

I really hope you have enjoyed the course, it has really been a great pleasure interacting with you and reading all your comments and questions. I have really enjoyed seeing how interested you have all been in the case, and how much discussion you have had about it each week. Thank you very much for joining us for the Introduction to Forensic Science MOOC, and don’t forget to cast your vote before 16:00 BST this Friday!

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This article is from the free online course:

Introduction to Forensic Science

University of Strathclyde