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Ask Penny

Please post your questions for this week in the comments section below. Penny will select the most liked/interesting questions and publish her response to these on this step by Wednesday of week 2.

First of all, I’d like to extend a very warm welcome to you all, and thank you for joining the Introduction to Forensic Science course. It’s great to see so many people from all across the world taking the course and getting involved with the discussions. Thank you for all of your great questions this week, and for all of the positive comments about how much you are enjoying the course. I wish that we had time to answer all of your questions but I’ve focused on those that were most popular and most closely related to my own area of knowledge, which is forensic biology, and in particular forensic genetics.

I’d also like to explain that there are some questions about the case that I’m not going to give you answers to just now, either because the answers will be revealed over the coming weeks, or because we want your knowledge and understanding of the case to develop alongside the evidence being presented to you. For similar reasons, we’re not going to tell you much about what we’ve changed about the case, as some people have asked. As you know, this case is based on a real case, and that case occurred in the 1980s. When we developed this course, we tried, for the most part, to replicate what happened in the real case as closely as possible, to give you as realistic an experience as we could. For this reason, there will be some things that may seem a bit strange to you, for example the fact that Mr Ward did not have mobile phone. However, it is worth noting that if this case had occurred more recently and mobile phones had been as widely used as they are now, the investigators would have been able to get a huge amount of information from Mr and Mrs Ward’s phones, either using triangulation to determine where the phones had been located, or by accessing phone records to see who the individuals involved in the case had been communicating with. In addition, we have sometimes used a little bit of artistic licence in places to make sure that we are able to introduce you to the different types of evidence that we wanted you to see.

Emma Rogoz asked about specialists such as entomologists and anthropologists in the UK, and whether they only work in particular jurisdictions or if they work on a national scale and join investigations wherever needed. The answer is that most experts in these specialist types of analysis are brought into investigations wherever and whenever they are needed, often all across the UK and overseas. Many of these specialists do not work full time on casework and will often be researchers and lecturers based in universities who assist with investigations from time to time.

Cynthia N asked about crime scene suits and whether these are used more than once or replaced/cleaned after each use. The answer is that scene suits are disposed of after being used once, because the risk of cross-contamination between scenes is too high to re-use the suits. Many forensic science laboratories are also moving towards using disposable lab coats as well, for the same reasons.

Dana Murray asked about the organisation of forensic science in universities and how it fits into university Departments/Faculties. Forensic science cuts across many different disciplines and so includes many areas of science. This means that it can be found in many different Departments or Faculties within universities, depending on what the focus of an individual forensic science section covers in terms of the topics being taught and researched by members of staff. Forensic science will often be found in a Science Faculty, but could come under biology or chemistry, or if the focus was more on forensic psychology then a Department might be found in a Humanities or Health Sciences Faculty. At the University of Strathclyde, the Centre for Forensic Science is found within the Science Faculty in the Department of Pure and Applied Chemistry, although around half of our academic staff are biologists.

Chaz McQueen asked about whether first responders have their DNA and fingerprints recorded so that they can be excluded from an investigation. There are a couple of different aspects to the answer to this. Firstly, all individuals who may come into contact with evidence in a case, e.g. police officers, paramedics, medical staff, crime scene investigators, and laboratory scientists will have a DNA sample taken and recorded in a staff/visitor elimination database, and usually any DNA profile generated in a case will be searched against this database to check for/detect any contamination. In addition, fingerprint databases may be kept containing fingerprints for all front-line police/crime scene staff whose fingerprints may be found at crime scenes. Secondly, if evidence such as footwear marks are found at a scene any individual who has been at the scene would have their footwear recovered for the purposes of elimination. Alexa Stokes asked about what would happen if the perpetrator is a police officer or paramedic, for example. Obviously, every case is different, but if an individual had been involved in committing a crime it is likely that multiple pieces of evidence indicating this would be recovered, and this would be difficult to explain as being an isolated contamination incident, so this should be investigated further.

Denise Walker asked about the amount of blood inside the car and whether a head injury would be expected to produce a lot more bleeding than is seen in this case. The amount of blood that would be expected at a scene depends on a lot of factors, including the mechanism by which the blood was shed. If someone is beaten repeatedly, for example with an iron bar, the blood vessels at the surface of their skin will be damaged and their heart will pump blood out through the damaged areas. If someone is stabbed and an artery is damaged, there will be a very forceful spray of blood from the arterial pressure up until the point that the heart stops and a victim dies. A gunshot to the head with no exit wound will result in instant death and so does not produce an injury that will bleed dramatically. We would therefore expect to see a relatively small amount of blood dripping from the wound, as is observed in the bloodstaining on Mrs Ward’s arm and the car seat.

Crawford Thomson asked about the interpretation of how and when DNA evidence came to be deposited at a crime scene, given advancements in DNA testing that mean we can now recover a full DNA profile from a handful of biological cells, or from ‘touch DNA’ found in secretions and cells shed from the surface of the skin. This is an excellent question, and something that is already beginning to affect the significance of DNA evidence, in some cases. Case context, or the information surrounding the events being considered in a case, is extremely important, and an investigator must always take this into consideration. Now that we can recover DNA profiles from very small amounts of material, and from surfaces that have been touched by individuals, we need to consider the possibility that we may be detecting ‘background DNA’ that is not related to the case. We also need to consider the possibility that the DNA transfer we see could be explained innocently, for example via social contact; two individuals who are in social (i.e. non-sexual) contact may have samples of DNA from each other present on their clothing or skin, or in their environment, and so the recovery of a DNA profile matching the other person may not indicate any criminal activity. In addition, we must also consider the possibility that DNA has been transferred via ‘indirect contact’, which can happen when DNA is transferred via an intermediary object. For example, one individual may deposit their DNA on a door handle when they touch it, and another individual subsequently touching that handle may pick up the first individual’s DNA on their hands and transfer that to another surface. If that surface is somehow associated with criminal activity i.e. the exterior surface of a gun used to shoot someone, then the first individual’s DNA may be recovered from that surface and implicate them in the crime, despite no direct contact with the gun.

Related to this, Cyndi Everetts asked about whether it is dangerous to believe that the current investigatory tool is 100% correct and infallible, and the answer is absolutely yes! This is seen frequently with DNA evidence, and often different members of the criminal justice system (e.g. police officers, prosecutors, jurors) will assume that if a DNA profile is recovered, the case is solved and they do not need to consider other evidence in the case, or alternative interpretations of the evidence - as seen in the example above this can be misleading. It is difficult to see an easy fix for this, but scientists need to be effective communicators of what their evidence means, and the criminal justice system needs to ensure that the people operating within that system are sufficiently educated to understand what the evidence means, as Alison Martin explained very clearly.

Suzanne Giblett asked about whether forensic scientists specialise in different areas, and the answer is yes. Although all types of scene are different, a crime scene manager will usually have very wide experience of all kinds of cases, and they will quickly identify what specialists are required in a given case and coordinate the work of these experts. For example, they may call in blood pattern specialists to examine the patterns of blood found at the scene of a violent crime to determine what type of action and force may have been involved, or if a firearm is involved in a case they may call in a firearms expert if the case requires it. In addition, specialised forensic medical examiners and forensic nurses are involved in dealing with the collection of evidence from individuals involved in sexual offences. In laboratories, most scientists will work within a reasonably specialised section, e.g. chemistry, drugs, DNA, biology, and they will focus on evidence types related to these specialisations.

A number of people also asked questions relating to decisions about putting up cordons around a crime scene, and how big these cordons are. For example, Mandy, Jackie David, and Rachel Evans all asked questions related to this, and Patience Usman’s question about the size of a crime scene tent is also relevant here. Deciding where to place cordons can be a very difficult decision depending on the specific circumstances of a case, and can be particularly difficult if the scene is outdoors and environmental conditions such as bad weather may threaten to compromise the scene. In general, two cordons are placed around a scene. The first is an inner cordon around the focal point of the scene, which can only be crossed by relevant scene personnel and specialists. This is tightly controlled and monitored by police using a scene log recording every single individual who goes in and out of a scene, and at what times. Secondly, an outer cordon is set up at what seems to be the limits of the scene, with more moderately controlled access. This provides a more general barrier to the general public and the media, but local residents or those with legitimate need to access the area would be allowed through. It can be very difficult to determine where the limits of a scene are, and quick decisions may have to be made about what to include within a scene. Sometimes a larger area will be selected and then reduced later if it is established that there is no evidence to be found in the larger area. However, there are obviously limits on this, and so sometimes a compromise will need to be made. Usually the cordons will be placed along natural barriers that restrict access or by putting up crime scene/police tape, and whilst the processing of a crime scene is ongoing a police officer will usually be controlling and monitoring access to the scene, particularly to the area within the inner cordon.

There were also some questions relating to outdoor crime scenes, how these are affected by environmental conditions and how this is managed. Elaine Willis, Paloma Gomes, Jo Corley and Patience Usman all asked questions relating to this topic. The answer will depend on the type of case being investigated, and for more serious crimes, more resources can be deployed more quickly. If weather conditions are bad, some measures can be taken to try and protect the scene and any evidence, such as tents. However, sometimes this is not possible and so the recovery of evidence must be prioritised in order to secure as much of it as possible before the conditions destroy it. The crime scene manager may need to make some very difficult and quick decisions about how to deploy resources and what to prioritise. This is also related to the question of how time affects the recovery and viability of evidence, and whether evidence remains viable if any significant period of time elapses between evidence being deposited and recovered. There are two factors to consider here. Firstly, the length of time that evidence would remain viable for analysis would depend on the conditions in which the sample had been stored. If a sample was at a crime scene that was outdoors, and there was a lot of rain, or very high temperatures or humidity, then samples of a biological nature such as DNA, body fluids and fingerprints could deteriorate and degrade very quickly, and this is a major challenge of managing a crime scene of this nature. However, if samples were indoors, in dry environments that were not subject to major fluctuations in temperature etc., then samples could still be analysed after months or even years. Deanne Tibbs’ question about Luminol testing of blood stains after long periods of time is also relevant here, and depending on the conditions that the blood has been under during that time, it is certainly possible that this could still be detected with tests such as Luminol. Secondly, over time after an incident has occurred, if a crime scene has not been secured then investigators would also have to consider the possibility that the scene may have become contaminated with material that is not related to the case. Depending on the circumstances of the case, it may still be valuable to search for and recover evidence, even after a considerable amount of time has passed, but it would be important to keep in mind that the crime scene could have been contaminated; this may also allow a defence team to introduce an element of uncertainty and doubt into a case.

Finally, there were multiple questions about crime scene managers and their role. For example, Jennifer Young, James Leggate, Dana Murray and David Palmer all asked questions about the CSM. The answer to many of these questions is “it depends”, and the specific details of a CSM’s position, roles and responsibilities will differ depending on jurisdiction, and to some extent the context of the case in question. In general, a CSM’s role is a very important one, and they are responsible for the initial assessment of a scene, planning the forensic strategy and agreeing this with the Senior Investigating Officer (SIO), briefing scene personnel and allocating appropriate numbers to individual aspects of scene examination (which will differ depending on the detailed requirements of the case, and the available resources), advising the SIO on the investigative potential of different evidence types and the value of using specialists (which will also depend on the detailed requirements of the case), and coordinating the individual experts within the overall scene (which can get logistically quite difficult). They are also responsible for managing the welfare of all scene personnel, carrying out health and safety risk assessments and implementing control measures. After the initial processing of the scene, the CSM is responsible for the ongoing coordination and implementation of the forensic strategy, advising the investigation team on the potential investigative value of different evidence types, planning and managing the forensic aspects of post mortem examinations, communicating findings from the scene and the forensic team to the investigation team, as well as maintaining ongoing communication between forensic laboratories, individual experts and the investigation team. If you are interested in finding out some more, then this article gives some further information about the role, as well as the skills and qualifications needed to become a CSM, and the career path that a CSM might follow.

- Penny

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This article is from the free online course:

Introduction to Forensic Science

University of Strathclyde