Forensic Entomology

Dr Dorothy Gennard is a principal lecturer in Forensic Science and co-ordinates the Forensic Entomology and Examination of Questioned Documents units. She is a member of the Royal Entomological Society and the World-Wide Dragonfly Association and a trustee of the British Dragonfly Society. Dr Gennard has close contact with the Lincolnshire Police Force and runs Forensic Entomology courses for the police and commercial forensic science companies.

List of Plates ix

List of Figures xiii

List of Tables xvii

Preface xix

Acknowledgements xxi

1 The Scope of Forensic Entomology 1

1.1 Forensic entomology in urban contexts 1

1.2 Stored product infestation and forensic entomology 2

1.3 Forensic entomology in the medico-legal context 3

1.4 The history of forensic entomology 6

1.5 Professional associations for forensic entomologists 9

1.6 The UK regulator for forensic science 10

1.7 Web addresses of relevant organisations 11

2 Forensic Entomology, DNA and Entomotoxicology 12

2.1 Preparation of specimens for molecular analysis 15

2.2 Methods of analysis and sources of information 16

2.3 Alternative methods 20

2.4 Validity of methodologies 21

2.5 The use of other molecular means of insect species determination 23

2.6 Insects and entomotoxicology 24

2.7 Forensic applications of arthropod behaviour for chemical analysis 27

3 Insects and Decomposition 29

3.1 Indicators of ‘time of death’ 29

3.2 Stages of decomposition of a body 30

3.3 Volatiles released from the body during decomposition 36

3.4 Decomposition in specific circumstances 38

4 Identifying Flies that are Important in Forensic Entomology 42

4.1 What is a fly and how do I spot one? 48

4.2 The fly lifecycle 53

4.3 Forensically important families of flies 60

4.4 Members of other orders that have forensic relevance in aquatic cases 73

4.5 Review technique: larval spiracles or mouthparts – preparation of whole slide mounts 75

5 Key for the Identification of European and Mediterranean Blowflies (Diptera, Calliphoridae) of Medical and Veterinary Importance – Adult Flies 77

5.1 Introduction 77

5.2 Key 80

6 Identifying Beetles that are Important in Forensic Entomology 82

6.1 What do beetles look like? 82

6.2 The life stages of the beetles 87

6.3 Selected forensically relevant families of beetles 88

6.4 Features used in identifying forensically important beetle families 89

6.5 Identification of beetle families using DNA 97

6.6 Key to selected forensically relevant families in the order Coleoptera 98

7 Sampling at the Crime Scene 101

7.1 Entomological equipment to sample from a corpse 101

7.2 Catching adult flying insects at the crime scene 104

7.3 The sampling strategy for the body 106

7.4 Sampling at aquatic crime scenes 108

7.5 Obtaining meteorological data at the crime scene 109

8 Rearing Insects and Other Laboratory Investigations 111

8.1 Transporting entomological evidence to the laboratory 111

8.2 Laboratory conditions for fly rearing 112

8.3 Methods of maintaining and rearing insects – terrestrial species 113

8.4 Dietary requirements of insects reared in the laboratory 116

8.5 Beetle rearing in the laboratory 117

8.6 Methods of maintaining aquatic species 119

9 Calculating the Post Mortem Interval 121

9.1 Working out the base temperature 123

9.2 Accumulated degree data 124

9.3 Calculation of accumulated degree hours (or days) from crime-scene data 127

9.4 Sources of error 128

9.5 Use of larval growth in length to determine post mortem interval (isomegalen diagrams and isomorphen diagrams) 130

9.6 Calculating the post mortem interval using succession 132

9.7 The effects of hymenopteran parasitoids on post mortem interval determination 137

9.8 Review technique: interpretation of data from a crime scene case study 137

9.9 Further reading 138

10 Ecology of Forensically Important Flies 139

10.1 Ecological relationships of some forensically relevant families 140

10.2 Specific family features 144

10.3 Fly infestation of the living 151

10.4 Flies influencing the crime scene 154

11 The Ecology of Some Forensically Relevant Beetles 156

11.1 Ecology of carrion beetles (Silphidae) 157

11.2 Ecology of skin, hide, and larder beetles (Dermestidae) 159

11.3 Ecology of clown beetles (Histeridae) 163

11.4 Ecology of chequered or bone beetles (Cleridae) 164

11.5 Ecology of rove beetles (Staphylinidae) 165

11.6 The ecology of dung beetles and related families 166

11.7 Ecology of ground beetles (Carabidae) 168

12 Investigations in an Aquatic Environment 169

12.1 Decomposition and submergence in water 170

12.2 The nature of the water bodies in which submergence may take place 176

12.3 Methods of establishing time since corpse submergence – indicator species 179

12.4 Attractants to the corpse 182

12.5 Methods of culturing aquatic insects 182

12.6 Algae an alternative source of determining time since submergence 182

13 The Forensic Entomologist in Court 184

13.1 The expert’s report 185

13.2 The content of the expert’s report 187

13.3 The forensic expert in the courtroom 194

13.4 Communicating entomological facts in court 195

13.5 Physical evidence: its continuity and integrity 195

13.6 The code of practice for experts 196

13.7 Use of single joint experts 198

13.8 Practical assignment – writing an expert report using the post mortem calculations generated from Chapter 9 198

13.9 Further reading on presentation in court 198

13.10 Web site addresses 199

Appendices 201

Glossary 205

References 216

Index 241