Activity 6.5 Crime investigation

Transcription

1 Purpose To explore the use of forensic techniques in an applied context. Body discovered A body has been discovered at a house in Redhill, Surrey. The body was found outside, near the house, and the immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. Experts investigate The crime is investigated by various forensic experts. You need to assign members of the group into each expert team and then, using the appropriate handouts and online resources provided, the members of each team must prepare a report to be presented at the investigation team meeting. PowerPoint presentation templates are provided to help in the preparation of some of the reports. You can access them from the interactive tutorial that accompanies this activity. Crime investigation team meeting At the investigation team meeting, appoint one member of the group to act as the Crime Investigation Officer. He or she must call on the experts to each present a report and then lead a discussion on the possible explanations for the death, based on the evidence presented. At the end of the meeting the team must try and decide what happened and who committed the murder. The experts and handouts available to each team are outlined in Table 1. Table 1 Expert team Forensic pathologist (one student) Scene of Crime Officer (one student) DNA analysis (small group) Entomologist (small group) Fingerprinting expert (small group) Crime Investigation Officer (one student) Handouts Forensic pathologist s brief Autopsy report Toxicology report SOCO brief SOCO PowerPoint for report DNA profile brief DNA profiling animation DNA profiling PowerPoint presentation Entomology briefing sheet Entomology PowerPoint presentation Fingerprint analysis briefing sheet Crime investigation officer briefing sheet In a larger class you might have two rival investigation teams. Do they both come to the same conclusion? The Crime Investigation Officer could be combined with the Scene of Crime Officer role and fingerprinting expert. This sheet may have been altered from the original. 1of 11

2 Forensic pathologist briefing document A body was discovered at a house in Redhill, Surrey on May The body was found outside, near the house, and the immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. As the forensic pathologist on the crime investigation team you need to present evidence for the cause of death of the deceased. You have the following to use to construct your evidence for cause of death: autopsy report blood test report from the toxicology lab. You will need to summarise the relevant findings and conclusions from your work at the crime investigation team meeting. Scene of Crime Officer (SOCO) briefing document Your work is mainly conducted at the scene of the crime. You will need to summarise the relevant findings and conclusions from your work at the crime investigation team meeting. You are the Scene of Crime Officer for a murder at a house in Redhill, Surrey. The body was found outside, near the house on May The immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. As the SOCO for this case you need to present a report at the crime investigation meeting detailing the evidence collected at the crime scene. You can give your report using the PowerPoint presentation available. The PowerPoint contains notes which can be seen by viewing or printing as notes pages. Crime Investigation Officer briefing sheet As the investigating officer you must chair the crime investigation meeting. You should ask for reports from the following forensic experts: Scene of Crime Officer (SOCO) Forensic pathologist Entomologists DNA profiling experts Fingerprinting experts. Ask the whole team to make notes on key points during the talks. You then lead a discussion about the possible course of events that led to the murder, and make a decision as a team about the course of action to be taken. Do you have a good case to present to the Crown Prosecution Service? Should you arrest anyone on suspicion of murder? This sheet may have been altered from the original. 2of 11

3 Autopsy report Autopsy on: Mr Patrick Barrett-Hughes Date of birth: 16/06/75 Address: Greyfriars, Whitepost Hill, Redhill, Surrey Date of death: Unknown Date autopsy: 13/05/09 PM done by: Dr U.C. D Eath Cause of death: Ruptured spleen and blood loss from abdominal stab wound. HISTORY Body was found on May at home address, outside, near a garage block. EXTERNAL EXAMINATION Body bloated and discoloured green/black over most of the surface. It is estimated 1 week to 10 days must have elapsed since death. Abrasions and small cuts were present on face and knuckles of right hand. There was a stab wound to upper left abdomen, which had bled profusely internally and externally. Bleeding shows that death took place up to 30 minutes after the stabbing. Weight: 98.3 kg Height: 184 cm INTERNAL EXAMINATION Central nervous system: Scalp Skull Meninges Middle ears Not examined Dural sinuses Vessels at base of brain Brain Spinal cord Not examined Respiratory system: Hyoid bone and larynx Trachea and main bronchi Pleural cavities Lungs (left, right) Both lungs were normal Diaphragm Cardiovascular system: Pericardial sac Heart Aorta and arteries Venae cavae and veins The aorta, innominate artery, carotid arteries and renal arteries contained some atheroma. The pulmonary arteries were normal. This sheet may have been altered from the original. 3of 11

4 Gastrointestinal system: Mouth, tongue, pharynx Oesophagus Stomach Duodenum Small intestine Large intestine Appendix Rectum Liver Gall bladder and biliary tree Pancreas Peritoneal cavity Genito-urinary system: Kidneys Ureters Bladder Prostate gland Testes The stomach contained a small quantity of clear liquid. The mucosa was normal. The liver tissue was normal. The capsule was intact. The renal capsules stripped easily to reveal normal renal surfaces. The renal cortex, medulla, calyces and pelvis of both kidneys were normal. Reticuloendothelial system: Spleen Ruptured capsule, resulting in extensive internal bleeding Lymph nodes Thymus gland fatty change Endocrine system: Thyroid gland Parathyroid glands Adrenal glands Pituitary Not examined Musculoskeletal system: The spinal column, ribs and pelvis were intact. Specimens retained: Blood sample. Comment: Dr U.C. D Eath BMEDSCI, MB ChB Forensic Pathologist This sheet may have been altered from the original. 4of 11

5 Blood test report from the toxicology lab Redhill and South Laboratory Toxicology Report 76 Wanefield Park Road Redhill Surrey Enquiries concerning this report should be directed to: Ms I.M. Analyst Case name: Mr Patrick Barrett-Hughes Report number: 2009/1762 Age: 34 Sex: M DoB: 16/06/75 SAMPLES RECEIVED TEST DONE ANALYTICAL FINDINGS Lab No. Date Time Type Compound Concentration Blood Cocaine Cocaine 0.6 mg l 1 Urine Drugs of abuse Cocaine Detected screen Cocaine metabolite(s) Detected Blood Cocaine Benzoylecgonine >1000 μg l l metabolite INTERPRETATION Following a recreational dose, blood cocaine concentrations are usually below 0.3 mg l l ; concentrations above 1 mg l l are often associated with serious toxicity. Benzoylecgonine (cocaine metabolite) was identified and quantified by immunoassay; concentrations above 500 μg l l are indicative of recent exposure to a recreational dose of cocaine. Note that cocaine is unstable in blood. No other drugs of abuse detected in the samples analysed within analytical limits. This sheet may have been altered from the original. 5of 11

6 DNA profiling briefing document A body has been discovered at a house in Redhill, Surrey on May The body was found outside, near the house, and the immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. As the expert on DNA profiling on the crime investigation team you need to present any evidence linking items from the crime scene with the people implicated in the crime. You have been given four samples for DNA analysis: 1 Victim s blood from body. 2 Blood from shirt found in outside rubbish bin at 35a, Garlands Rd on May 11 during police search. 3 Cheek cell sample from Mr A. Gifford, sole resident of 35a, Garlands Rd. 4 Hair found in wrappings around cocaine in briefcase found at 35a, Garlands Rd. You have given the samples to your laboratory assistants to run genetic profiles. You instructed your assistants to amplify the DNA samples using PCR and suggested that they analyse three satellites, which in this case should be sufficient to match the forensic samples with the blood of either of the two individuals. Go to the interactive tutorial (DNA analysis simulation) that accompanies this activity. This will allow you to find the results of the DNA analysis of the samples. Prepare a report explaining your findings and your conclusions. There is a PowerPoint template with some images that may help in your presentation. You need to remember that the detectives you are addressing will not necessarily be familiar with DNA profiles. You will have to explain the following: The peaks on the DNA profile represent the alleles of non-coding DNA called STRs selected for analysis. The alleles for each STR have different numbers of repeat sequences, so are different lengths. The DNA from a sample is prepared so that the alleles can be separated by electrophoresis. As any individual has two copies of each gene, there will be two peaks for each gene if the individual is heterozygous, and one peak if the individual is homozygous. The three STRs you have selected to analyse have 7, 10 and 13 possible alleles respectively (i.e. the number of different repeat sequences in the STRs), so there is only an extremely small chance of two individuals having exactly the same combination of alleles for all three genes. You may wish to revisit the PCR animation in Activity 6.4 so you can summarise briefly how it is possible to use such small forensic samples, such as the hair in this case. This sheet may have been altered from the original. 6of 11

7 Forensic entomologist briefing document A body has been discovered at a house in Redhill, Surrey. The body was found on May outside, near the house, and the immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. As the forensic entomologist on the crime investigation team you need to present evidence for the estimated time of death of the deceased. You have also been given some maggots from a blood-stained shirt that was found at a nearby address, but may be connected with the death. The shirt was found outside in the bin, wrapped in a plastic bag. You have the following to use to construct your evidence for time of death: Average temperature data for May The average temperature for the week before the body was found can be calculated from this. Diagrams of some preserved maggots taken from the body at the crime scene. Diagram showing length of Calliphora vicina with age for different temperatures. Graphs showing emergence of adults from maggots from the body and from a bloodstained shirt that may be linked with the murder. The maggots have been incubated on liver until emergence of adults, so as to simulate the conditions where the dead body was found. The maggots were incubated at the average temperature for the week before the body was found. You need to do the following: Calculate the average temperature for the period 4 10 May, i.e. the period of a week before the body was found. Round up to the nearest whole C. This is the temperature used to incubate maggots found on the body and shirt. Measure the length of the maggots, and use the graph of length variation over time with temperature to estimate the age of the maggots. Use the average temperature you have calculated above and the line for the measured maggot length to read the age of the maggot from the x-axis. Calculate the estimated date of death, using the time for a complete life cycle (as discovered from incubation of the second generation), and the dates of emergence of the first adults from each sample. The time between eggs being laid on the dead body and discovery of the body can be calculated using the formula: (time taken for complete life cycle) (time time of discovery of = taken for emergence of first adults from body after egg laying the maggots found on the body) It is assumed that this gives an approximate estimate of time of discovery of the body after death. Does this agree with the estimated age of the maggots using their length? You need to account for the difference in the apparent age of the maggots from the nostril and those from the body and shirt. Find out what factors can accelerate maggot development so that you can make suggestions. If you want to suggest any toxicology tests are performed on the body, ask the lab performing the autopsy to do this for you. You need to present your findings to the next crime investigation team meeting. There is a PowerPoint presentation with some pictures and data that should help as a basis for your presentation. C. vicina complete life cycle determination The adults emerging from the maggots found on the body and shirt were allowed to lay eggs on a fresh liver sample. The eggs were incubated in conditions to simulate the environment of the dead body to find the time required for a complete life cycle. The C. vicina second generation adults first started to emerge after exactly 28 days. This sheet may have been altered from the original. 7of 11

8 Table 1 Average temperature data for Date in May Average daily temperature/ C Mon 1st 7.25 Tues 2nd 7.30 Wed 3rd 8.25 Thurs 4th 7.85 Fri 5th 5.30 Sat 6th 9.85 Sun 7th 12.2 Mon 8th 9.95 Tues 9th Wed 10th Thurs 11th Fri 12th Sat 13th Figure 1 Average daily temperature: May Figure 2 Length of maggots taken from body. Figure 3 Diagram showing how length of Calliphora vicina varies with temperature over time. Each line is for a measured maggot length in mm. Lines to the right of the dots are lengths of post-feeding maggots. This sheet may have been altered from the original. 8of 11

9 Figure 4 Calliphora vicina emergence data. The maggots from the body and bloodstained shirt were incubated on liver at the temperature calculated as the average for the period before the body was found. The graphs show the emergence of adults from the maggots. This sheet may have been altered from the original. 9of 11

10 Fingerprint expert briefing document A body has been discovered at a house in Redhill, Surrey on May The body was found outside, near the house, and the immediate cause of death was thought to be a stab wound to the abdomen. From the state of decomposition of the body it would appear the victim had been dead for at least a week when discovered. As the fingerprint expert on the crime investigation team you need to present evidence matching either the deceased (Mr Patrick Barrett-Hughes) or the main suspect (Mr Anthony Gifford) to other items from the crime scene. You have a selection of fingerprints from the crime scene, along with ten print fingerprint cards taken from Mr Patrick Barrett-Hughes, and the prints of Mr Anthony Gifford from the central records department. Each member of your team can be given one crime scene fingerprint to match. Sixteen or more matching points should be found in order to confirm the match between a crime scene print and one of the people implicated in the crime, but fewer are accepted in court if the expert considers the features to provide sufficient evidence of a match. Use the weblinks that accompany Extension 6.1 to find any more information you need about fingerprint matching. You need to make a short presentation to the crime investigation team, summarising any conclusions you come to about the fingerprints you have been given to match. The images of the fingerprints can be found in the mediabank on the website, and can be downloaded for use in a PowerPoint presentation. Matching fingerprints The basic fingerprint patterns must first be matched and then the point details are identified. Figure 1 Fingerprint patterns. Fingerprints Figure 2 An example of eleven features to be used in point matching of this fingerprint. This sheet may have been altered from the original. 10 of 11

11 Left hand: Mr Anthony Gifford Little finger Ring finger Middle finger Index finger Thumb Right hand Mr Anthony Gifford Thumb Index finger Middle finger Ring finger Little finger Left hand: Mr Patrick Barrett-Hughes Little finger Ring finger Middle finger Index finger Thumb Right hand: Mr Patrick Barrett-Hughes Thumb Index finger Middle finger Ring finger Little finger Prints from the money package found in Mr Patrick Barrett-Hughes jacket pocket. - Print from the briefcase containing cocaine found at 35a. Garlands Road, Redhill. This sheet may have been altered from the original. 11 of 11