Forensic Science: Fundamentals & Investigations, 2e Chapter 2. All rights Reserved Cengage/NGL/South-Western 2016

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1 1 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

2 Crime-Scene Investigatin and Evidence Cllectin By the end f this chapter yu will be able t: 2.1 Summarize Lcard s Principle f Exchange. 2.2 Identify fur examples f trace evidence. 2.3 Distinguish between direct and circumstantial evidence. 2.4 Identify the types f prfessinals wh might be present at a crime scene. 2.5 Summarize the seven steps (seven S s) f a crime-scene investigatin. 2 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

3 Crime-Scene Investigatin and Evidence Cllectin By the end f this chapter yu will be able t: 2.6 Explain the imprtance f securing the crime scene. 2.7 Identify the methds by which a crime scene is dcumented. 2.8 Demnstrate prper technique in cllecting and packaging trace evidence. 2.9 Explain what it means t map a crime scene Describe hw evidence frm a crime scene is analyzed. 3 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

4 Vcabulary chain f custdy first respnder circumstantial evidence individual evidence class evidence paper bindle crime-scene investigatin crime-scene recnstructin datum pint direct evidence primary crime scene secndary crime scene trace evidence triangulatin 4 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

5 Principle f Exchange Lcard's Principle f Exchange When a persn cmes in cntact with an bject r anther persn, a crss-transfer f physical material can ccur. The intensity, duratin, and nature f the entities and cntact determine the extent f the transfer. 5 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

6 Types f Evidence Direct evidence First-hand bservatins Circumstantial evidence Indirect evidence that can be used t imply a fact but that des nt prve it 6 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

7 7 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

8 Types f Evidence (cntinued) Class evidence Narrws an identity t a grup f persns r things Individual evidence Narrws an identity t a single persn r thing 8 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

9 The Crime-Scene Investigatin Team Plice fficers Crime-scene investigatrs Medical examiners Detectives Specialists 9 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

10 The Seven S S f Crime-Scene Investigatin 1. Securing the Scene 2. Separating the Witnesses 3. Scanning the Scene 4. Seeing the Scene 5. Sketching the Scene 6. Searching fr Evidence 7. Securing and Cllecting Evidence 10 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

11 11 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

12 Packaging Evidence The paper bindle is ideal packaging fr small, dry, trace evidence. 12 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

13 Chain f Custdy 13 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

14 14 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

15 Mapping the Outdr Crime Scene Datum Pints and Subdatum Pints 15 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

16 Mapping the Outdr Crime Scene (cntinued) Marking Evidence Cllecting Limits 16 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

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18 18 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

19 Mapping the Outdr Crime Scene (cntinued) Measuring and Marking Evidence Psitins 19 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

20 Analyze the Evidence Frensic lab technicians are specialized t prcess nly ne type f evidence. 20 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

21 Crime-Scene Recnstructin Crime scene recnstructin invlves: Frming a hypthesis f the sequence f events frm befre the crime was cmmitted thrugh its cmmissin Cmparing the evidence t witnesses statements Investigatrs need t maintain an pen mind as they examine all pssibilities. 21 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

22 Staged Crime Scenes Cmmnly staged types f crime scenes include: Arsn Murder staged t lk like a suicide Burglary 22 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

23 Summary Lcard s Principle f Exchange states that cntacts between peple and bjects during a crime can result in a transfer f material. Evidence may be direct, as in eyewitness accunts, r circumstantial, which des nt directly supprt a fact. Evidence may be physical r bilgical. Trace evidence is a small amunt f physical r bilgical evidence. 23 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

24 Summary (cntinued) A crime-scene investigatin team cnsists f plice fficers, detectives, crime-scene investigatrs, medical examiners, and specialists. A crime-scene investigatin cnsists f recgnizing, dcumenting, phtgraphing, and cllecting evidence frm the crime scene. First-respnding fficers must identify the extent f a crime scene, including primary and secndary scenes when pssible, secure the scene(s), and segregate witnesses. 24 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016

25 Summary (cntinued) After examining the crime scene(s) and identifying evidence, the crime-scene investigatrs dcument the scene(s) with phtgraphs and sketches. Crime scene(s) are smetimes precisely mapped t ensure that n evidence is verlked. Evidence must be prperly handled, cllected, and labeled s that the chain f custdy is maintained. Evidence is analyzed in a frensic labratry, and the results are prvided t detectives, wh develp a pssible crime-scene scenari. 25 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016