Unit 3: Forensic science (LEVEL 2)

Transcription

1 Unit 3: Forensic science (LEVEL 2) Learning outcomes By completing this unit candidates will develop knowledge and understanding of how to conduct a forensic investigation. Candidates will be able to collect and analyse materials and information. They will also be able to evaluate the data in order to draw conclusions. Candidates will produce evidence to meet the unit assessment objectives in order to show that they understand: how to plan a forensic investigation techniques for examining crime scenes and collecting evidence techniques for examining the evidence how to interpret their findings correct method for presenting their results. Assessment objectives 1 Prepare to carry out a forensic investigation 2 Undertake specialist crime scene examinations 3 Carry out laboratory examination Knowledge, understanding and skills Initially the requirements of the investigation need to be established: circumstances of the incident and the scene are ascertained from relevant sources determine the steps needed to undertake the investigation identify the equipment and prepare its use to undertake the investigation consider the health and safety requirements and what precautions need to be taken understand why forensic investigations depend on following standard procedures Carry out examination which ensures detection of all types of potential evidence: identify the area of the scene, mark it out and protect it to preserve the scene locate, identify and collect evidence handle, package and record evidence preserve evidence ensuring its integrity and preventing contamination or degradation record relevant information accurately and comprehensively Carry out simple forensic examination of materials and objects in a laboratory using a minimum of THREE tests, with no more than ONE from each subject area: use visual examination and measurement for comparative analysis microscopically examine objects identify materials by chemical analysis identify materials by physical analysis identify materials by biological analysis OCR Level 2 Nationals in Science 1

2 Assessment objectives 4 Describe different types of instrumental analysis Knowledge, understanding and skills Understand the use of more complicated instrumental analysis that may used by the professional Forensic Scientist: gas chromatography high performance liquid chromatography mass spectroscopy infra-red spectroscopy electrophoresis/dna fingerprint blood typing microscopical examination 5 Interpret findings Record and collate results accurately in a clear format: record relevant information accurately comment on the accuracy, reliability and limitation of results use sufficient results from specified examinations summarise the results to meet examination requirements 6 Report findings Report the findings of the forensic examinations: establish the type, scope and purpose of the report clearly explain the findings and their interpretation in the context of the case based on the results consider alternative explanations Use ICT sources or tools to either gather or present data Assessment This unit is centre-assessed and externally moderated. In order to achieve this unit candidates must produce a portfolio of evidence showing that they can meet all of the assessment objectives. Portfolios of work must be produced independently. They will need to be made available, together with witness statements and any other supporting documentation, to the OCR Visiting Moderator when required. Centres must confirm to OCR that the evidence produced by candidates is authentic. An OCR Authentication Form is provided in the Centre Handbook and includes a declaration for assessors and candidates to sign. It is a requirement of the QCA Common Criteria for all Qualifications that proof of authentication is received. Guidance on assessment and evidence requirements The aim of this unit is to extend candidates knowledge and experience of practical techniques through an interesting vocational context, which covers aspects of biology, chemistry and physics. Although the context in this unit is forensic science based, candidates should realise that the procedures and techniques are applicable to a wide range of disciplines and careers. 2 OCR Level 2 Nationals in Science

3 Tutors should at all times make sure that candidates comply with any safety considerations that have been published by any regulatory body (refer to COSHH regulations, CLEAPPS handbook and CLEAPPS: hazard and student safety sheets), there may also be relevant safety regulations issued by the DfES or local LEAs as well as the institution that the course is being carried out in, that need to be considered. Candidates learn how analytical and investigative methods can be used to answer questions, solve problems, and gain insight into the work of professional scientists. They have the opportunity to develop practical skills, powers of deduction and to interpret results using standard procedures in a logical sequence. Wider skills should be encouraged, with groups sharing investigating work and discussing possible interpretations, to encourage stronger teamwork. There should also be opportunities for candidates to develop wider communication skills, depending upon the format of their portfolios. The main focus of this unit is for the candidates to carry out the forensic process in a crime scenario with items of evidence mostly pointing towards the same conclusion, but some evidence should give contradictory results. This is realistic and should help to avoid candidates jumping to conclusions. Candidates should also demonstrate a broader understanding than can be gained from just one investigation. This may require candidates to place a greater range of evidence in their portfolio than just the specific material from one forensic investigation. An OCR model assignment is available for this unit. It can be downloaded from our website: and can also be found in the Model Assignments folder on this CD Rom. Prepare to carry out a forensic investigation (AO1) Candidates need to establish the details of the incident and then plan their investigation. They should realise that each investigation follows a sequence known as the forensic process and understand the importance of each stage. The stages are: undertake crime scene examination collect evidence analyse the evidence interpret the results prepare a report. To carry out this process, candidates will need to follow standard procedures and to identify the appropriate equipment, which has the sensitivity and accuracy to perform reliably. Candidates may need to practice, to be able to use the equipment effectively. They should ensure all equipment is clean, to avoid contamination, and calibrated prior to use. At all times the candidates must consider health and safety requirements and the precautions that need to be taken, when carrying out their investigation. These health and safety issues extend to the crime scene, the procedures that candidates carry out and the materials that they use, both at the scene and in the laboratory. Candidates should be aware that individual tasks carried out by forensic scientists all follow standard procedures and they should understand why this is necessary. To demonstrate the ability to sequence an investigation, candidates should produce a plan of action to carry out the investigation. OCR Level 2 Nationals in Science 3

4 Undertake specialist crime scene examinations (AO2) Candidates need to know how forensic evidence is collected ensuring detection of all types of potential evidence. They must: identify the area of the scene, mark it out and protect it to preserve it. Police tape is often used to delineate a crime scene and keep people away from it. Tents are also often used to protect the scene from the weather agree and establish who has access to the scene taking account of potential contamination and loss of evidence decide on the precautions that need to be taken when collecting forensic evidence. For example, protective clothing (suit, hood, gloves, footwear) is worn and clean equipment is used (forceps to pick up evidence) for collecting evidence in a labelled bag understand why precautions are taken: to ensure that evidence samples are not contaminated by the forensic examiner or with materials from the environment (fibres, hair, DNA, etc). Before the evidence is collected the scene needs to be searched logically, the sequence of which may depend on the size and location of the scene. Generally the area is mapped into a grid and then a preliminary search is made, followed by a detailed search when the position of evidence recorded. Candidates may have seen from television crime programmes how a general visual or ultra-violet sweep is made, which is then followed up by a hands and knees search for evidence. When evidence is located, it is numbered and its position recorded by sketching a diagram or photographing. To demonstrate this approach to a crime scene, candidates could, within their plan of action, say how they are to carry out a crime scene investigation, and explain why they will take precautions to protect the evidence. At Level 2, it would not be expected for candidates to use reagents to detect hidden evidence or have specific instrumentation used by Police such as breath testers. However, candidates need to know how to collect examples of evidence and to choose the appropriate method for a specific crime scene. For example: fingerprints candidates need to know that there are different types of prints (latent, plastic, etc). They also need to know about different methods of collection, depending on the surface they are found upon (dust with carbon powder on pale surfaces blowing off excess powder and lifting the print with Sellotape etc) footprints and tyre prints (construct a dam around the print, then pour in Plaster of Paris, allow cast to dry and lift and clean) fibres and hair can be lifted using Sellotape liquids can be lifted by swabbing. When the evidence has been collected it should be packaged, sealed, labelled and recorded in sealable plastic bags that prevent contamination and loss of evidence. Consideration must also be given to how the collected evidence is transported and stored. In actual crime incidents evidence may have to be stored for years, so it must stored in a manner that ensures its integrity and reduces loss and degradation. To demonstrate this information gathering candidates could compile a table of standard procedures from secondary sources. 4 OCR Level 2 Nationals in Science

5 Carry out laboratory examination (AO3) Most forensic data is obtained by examining materials and objects in a laboratory. To obtain accurate, reliable results using very small amounts of samples, forensic scientists use a range of instrumental techniques. Candidates are not expected to use these, but they do need to realise their greater accuracy and sensitivity, the purpose of each technique and know what type of information they provide. Candidates need to be aware that the samples they investigate, and techniques they use, are deliberately simplified. Candidates need to be able to carry out the following procedures to examine forensic evidence, analyse and interpret it, and draw conclusions: Microscopical examination and measurement fingerprints - name (loop, arch or whorl), and match crime scene with the suspects fibres and hair - match samples, compare cut ends of fibres paint samples - examine paint layers and draw conclusions pollen grains - compare and match foot/tyreprints - describe the type of evidence provided directly by these eg for shoes, size, make, tread, specific pattern of wear; for ballistics they need to know about matching the bullet with the gun, and bullet with cartridge case glass - be able to piece together glass fragments and compare samples. Physical properties of the glass such as transparency and refractive index might also be measured and used in comparison with secondary data. Chemical analysis detect Na+, K+, Ca2+, Cu2+, Pb2+, Fe3+, Cl-, SO42- and CO32- using: Flame tests Metal Calcium Copper Sodium Potassium Flame colour brick red blue green yellow lilac Ion tests: Ion Test Result Chloride Add silver nitrate solution White precipitate Sulphate Add acidified barium chloride solution White precipitate Carbonate Add dilute acid & test gas given off with limewater Milky white precipitate Copper Add sodium hydroxide solution Blue gel precipitate Iron Add sodium hydroxide solution Brown precipitate Lead Add sodium chloride solution Off-white precipitate that dissolves on heating OCR Level 2 Nationals in Science 5

6 measure acidity/alkalinity using a ph meter (calibration of the instrument would need to be carried out) detect ethanol by its effect on acidified potassium dichromate solution, turning it from orange to blue green. Chromatography use paper and/or then layer methods separate coloured mixtures eg inks. Instrumental techniques gas chromatography (GC) for any mixture that can be vaporised without damaging it, eg accelerants, drugs, etc high Performance Liquid Chromatography (HPLC) liquid chromatography for mixtures of more delicate molecules, eg drugs mass spectroscopy (or mass spectrometry, MS) GC and HPLC cannot positively identify substances; MS can. Molecules are split into charged fragments that separate according to mass. The molecule is then pieced together infra-red spectroscopy for identifying specific organic molecules, eg alcohol. For grading purposes there is an expectation that candidates will carry out a minimum of three tests, with no more than one from each subject area. Describe different types of instrumental analysis (AO4) Forensic scientists have a number of instrumental analysers that have a far greater sensitivity than the tests that candidates have access to. Although candidates will not use these themselves, they need to be aware of them and their importance. Higher level candidates would be expected to discuss the instrumental techniques when evaluating the limitations of their own testing. Interpret findings (AO5) Candidates need to summarise and assess their examinations, interpreting the results and drawing conclusions, prior to the preparation of a final report. The opinions drawn will be informed by databases and historical data. Candidates need to know what type of information is stored in databases, to collect evidence. They should also be aware that mismatches are equally important for elimination purposes. Such databases might include: the DVLA database, based at the DVLC in Swansea genetic profiles database criminal records medical records and dental records fingerprint records biological records, describing pollens, seeds, insects etc. 6 OCR Level 2 Nationals in Science

7 Having completed their investigation, candidates need to appreciate the difference between the scientific facts that they have established, and the inferences that can be drawn from these in relation to the crime. They should be encouraged to draw together the various strands of evidence and to consider whether or not particular pieces of evidence support a proposed theory about the crime. Candidates should realise that evidence that does not fit their particular theory must still receive due consideration, and it is important that such evidence is built into the original scenario. Candidates may produce evidence for their portfolio in various forms: laboratory notes describing investigations and presenting the information in appropriate ways, eg diagrams, tables, graphs items of evidence (Exhibit A etc) which may be: o o o o actual objects from the scene of crime pictorial, eg photographs or drawings fingerprints or plaster casts experimental evidence. a spoken statement describing the facts, supported by a witness statement written summary notes to help while making a statement witness statements. Report findings (AO6) Candidates must establish the type, scope and purpose of the report. Reports will be seen by a wide range of individuals most of whom will have little scientific knowledge. They must therefore be clear and as unambiguous as possible. They should clearly explain the findings and their interpretation in the context of the case based on the results. This can be done by: outlining the background of the incident explaining the requirement of individual for whom the report is intended describing the examinations conducted and their outcomes making an assessment of the examination results. Candidates should consider alternative explanations, as the evidence may be interpreted in a different way. Presenting the report lends itself to many different methods of communication. Part of the presentation may be oral and candidates may be asked to justify their interpretations. This may be as a mock trial with prosecuting and defence teams, or presented as a TV programme, but whatever way is used the centre must ensure that candidates have evidence for their portfolios. The presentation could be recorded onto video/dvd/movie clip and submitted with the candidate s portfolio. Ideally, during delivery, candidates should be made aware of how the procedures and techniques of the forensic process can be applied to most other scientific disciplines. This will give candidates an opportunity to appreciate career choices within science, outside the field of Forensic Science. Candidates must use ICT sources or tools to either gather or present their data. OCR Level 2 Nationals in Science 7

8 Signposting to Key Skills The unit contains opportunities for developing the Key Skill, and possibly for generating portfolio evidence, if teaching and learning is focused on that aim. Assessing staff will need to check each candidate s evidence against the specifications to ensure all evidence requirements have been met. Additional evidence may also be required. Key Skill reference Key Skill reference Key Skill reference C2.1 N2.1 ICT2.1 C2.2a N2.2a ICT2.2 C2.2b N2.2b ICT2.3 C2.3 N2.2c N2.2d N2.3 Mapping to National Occupational Standards Occupational Standards Unit number Title LATA 1.01 Complying with Statutory regulations and Safety requirements LATA 1.04 Take laboratory measurements LATA 1.05 Perform basic laboratory activities LATA 2.03 Carry out simple testing operations LATA 2.04 Carry out simple sampling operations LATA 2.05 Prepare laboratory materials, equipment and resources LATA 2.06 Calibrate equipment LATA 2.13 (Cogent 1.8) Work in aseptic or clean room conditions Forensic Science 1 Prepare to carry out examinations Forensic Science 2 Examine items and samples Forensic Science 3 Undertake specialist scene examinations Forensic Science 4 Interpret findings Forensic Science 5 Report findings Resources The following are suggestions of resources that could be useful when delivering the unit. They are neither prescriptive nor exhaustive, and candidates should be encouraged to gather information from a variety of sources. Books DfES (1996) CLEAPSS Laboratory Handbook (updated 2005) Safety in science education The Stationery Office Books See URL: for details 8 OCR Level 2 Nationals in Science

9 CLEAPSS Hazcards (updated 2005) Association for Science Education (1996) Dept of Education and Science (1985) Ramsden, EM. (1996) McCarthy, A. (1997) White, P.C. (editor) (2004) Kind, S.S. (1987) Fisher, B., Svensson, A. & Wendel, O. (2000) Faust, C.B. (1992) See URL: for details Safeguards in the school laboratory ASE Microbiology: A guide for schools and nonadvanced further education The Stationery Office Books Detection and analysis (A Level Chemistry) Nelson Thornes Methods of analysis and detection Cambridge University Press Crime scene to court: The essentials of Forensic Science The Royal Society of Chemistry Scientific investigation of crime Forensic Sci. Services Techniques of crime scene investigation CRC Press Modern chemical techniques The Royal Society of Chemistry The accompanying RSC video, Modern Chemical Techniques, comprises 12 four five minute clips of instruments in use. These allow candidates to view the instruments without being overwhelmed by technical details, which are given in the book, rather than on film. Details of analytical methods, including instrumental techniques, can be found in Advanced GNVQ and GCE texts, together with examples of their applications. Though these applications are not normally related to forensic science, it should not be difficult for candidates to appreciate how the techniques can be used for this purpose. Journals/Magazines/Newspapers Protocols and standard operating procedures from local organisations. Science teachers should be familiar with the requirements of COSHH Regulations, with DfEE (DES) memoranda on the use of plants and animals in schools and with regulations applying locally. For information contact science advisor/education department. Websites CRAC Career development for life. URL: The Careers Research and Advisory Centre aims to advance the education of the public, and young persons in particular, in lifelong career-related learning. OCR Level 2 Nationals in Science 9

10 Grading Assessment Objective Pass Merit Distinction AO1 Prepare to carry out a forensic investigation Candidates produce a brief plan which outlines how they plan to undertake their forensic investigation, including health and safety considerations. Their plan contains a basic structure and they may need guidance on the choice of appropriate forensic tools. Candidates produce a detailed plan which outlines how they plan to undertake their forensic investigation, including health and safety considerations. Their plan contains a clear structure and they need limited guidance on the choice of appropriate forensic tools. Candidates produce a comprehensive plan which outlines how they plan to undertake their forensic investigation, including health and safety considerations. Their plan is very well structured and they need no guidance on the choice of appropriate forensic tools. AO2 Undertake specialist crime scene examinations Candidates undertake crime scene examination and identify some of the possible forensic evidence. Candidates sometimes collect and store evidence in the most appropriate manner. Evidence is often degraded or crosscontaminated. Candidates undertake a detailed specialist crime scene examination and identify most of the possible forensic evidence. Candidates usually collect and store evidence in the most appropriate manner and the possibility of degradation or crosscontamination of evidence is low. Candidates undertake an extensive specialist crime scene examination and identify all of the possible forensic evidence. Candidates always collect and store evidence in the most appropriate manner and the possibility of degradation or crosscontamination of evidence is very low. AO3 Carry out laboratory examination Candidates carry out three forensic tests and demonstrate basic competence in their use. They also comment in basic terms on the reliability and validity of the testing procedures. Candidates carry out a minimum of three forensic tests and demonstrate competence in their use. They also comment in detail on the reliability and validity of the testing procedures. Candidates independently carry out a greater range of tests and are highly competent in their use. They also comment in great detail on the reliability and validity of the testing procedures. Their evidence is well structured. 10 OCR Level 2 Nationals in Science

11 Assessment Objective Pass Merit Distinction AO4 Describe different types of instrumental analysis Candidates describe four different types of forensic instrumental analysis and demonstrate a basic appreciation of the advantages and disadvantages of using each of these. Candidates describe at least four different types of forensic instrumental analysis and demonstrate a good appreciation of the advantages and disadvantages of using each of these. Candidates describe at least four different types of forensic instrumental analysis. They demonstrate a thorough appreciation of the advantages and disadvantages of using each of these and compare and evaluate the types of tests that can be conducted in an educational institution with those used in the commercial world. Their evidence is well structured. AO5 Interpret findings Candidates record and collate their results. They sometimes record the relevant information clearly and they comment briefly on the accuracy, reliability and limitations of their results. Candidates record and collate their results. They generally record the relevant information clearly and they comment on the accuracy, reliability and limitations of their results. Candidates record and collate their results. They always record the relevant information clearly and comprehensively. They also comment on the accuracy, reliability and limitations of their results in detail. AO6 Report findings Candidates report the findings of their forensic science examination and provide a brief analysis of their results which considers some alternative interpretations. Candidates use ICT sources or tools to either gather or present their data. Candidates report the findings of their forensic science examination and provide a detailed analysis of their results which considers many alternative interpretations. Candidates use ICT sources or tools to either gather or present their data. Candidates report the findings of their forensic science examination and provide an extensive analysis of their results which considers most alternative interpretations. Candidates use ICT sources or tools to either gather or present their data. OCR Level 2 Nationals in Science 11