Chapter 2 The Crime Scene

1. Chapter 2The Crime Scene

2. Physical Evidence • Crime laboratories run on physical evidence. • Physical evidence includes any and all objects that can establish that a crime has been committed . • It can also provide a link between a crime and its victim or a crime and its perpetrator. • If physical evidence is to be used effectively for investigator, it must be first recognized at the crime scene.

3. Securing the Crime Scene • In order to be useful, evidence at a crime scene must be preserved and recorded in its original condition as much as possible. • The first officer to arrive at the scene is responsible for securing the crime scene. • First priority should be given to obtaining medical assistance for individuals in need and to arresting the perpetrator.

4. Extensive efforts must be made to exclude all unauthorized personnel from the crime scene. • Once the crime scene is secured, the initial walk through must begin. • Recording the crime scene is a critical piece to the investigation process.

5. Recording the Crime Scene • Photography, sketches, and notes are the 3 methods for crime-scene recording. • Sometimes, limitations may prohibit the use of photography at a crime scene. • The crime scene should always be recorded in its original state.

6. Photography • The most important thing for photographing a crime scene is for it to be in an unaltered condition. • Unless there are injured people involved, objects must not be moved until they have been photographed from all necessary angles. • As items of evidence are discovered, they are photographed to show their position and location relative to the entire scene. • Videotaping has become increasingly popular with technological advancements.

8. Sketches • Once photographs are taken, the crime scene investigator will sketch the scene. • Rough sketch- A draft representation of all information and measurements at crime scene. It shows all items of evidence, as well as other important features. • Finished Sketch- A precise drawing of the crime scene, usually drawn to scale. This is not normally done at the crime scene. • Unlike the rough sketch, the finished sketch is drawn with accuracy and detail.

10. Notes • Note taking must be a constant activity through the crime scene. • These notes must include a detailed written description of the scene with the location of items of evidence recovered. • The must identify: - the time an item of evidence was discovered - by whom -how and who packaged and marked it - the disposition of the item after it was collected.

12. Recording the Crime Scene • Investigators only have a limited amount of time to work a crime scene in its original state. • The opportunity to permanently record the original scene must not be lost. • Original recordings are required for presentation at a trial in order to document the condition of the crime scene and to show the location of evidence. • Every step of the investigation should be documented thoroughly.

13. The Preliminary Exam • A lead investigator will start the process of evaluating the area. • First, the boundaries of the scene must be determined. • Next, they establish the perpetrator's path of entry and exit. • They then proceed with an initial walk-through of the scene to gain an overview of the situation and to develop an examination method of the entire crime scene. This is done before processing the crime scene for evidence

14. The Search • The search for evidence at a crime scene must be thorough. • The search pattern depends on the size and location of the scene, and the numbers of collectors. • The investigator must not overlook any pertinent evidence. • Physical evidence can be anything from massive objects to microscopic traces. • Items of evidence can be clearly visible, or only detected at a crime lab through examination. • It is important to collect all possible carriers of trace evidence (clothing, vacuum sweepings, fingernail scrapings).

15. Beyond the Crime Scene • The search for physical evidence must extend beyond the crime scene to the autopsy room. • Here, the medical examiner or coroner will examine the victim to establish cause and manner of death. • Tissues and organs will be retained for pathological and toxicological examination. • A variety of items that may be obtainable from the body must be secured at this time.

16. The following are to be collected and sent to the forensic laboratory: 1. Victim’s clothing 2. Fingernail nails 3. Head and pubic hairs 4. Blood (for DNA typing) 5. Vaginal, anal, and oral swabs (in sex-related crimes) 6. Recovered bullets from the body 7. Hand swabs from shooting victims (for gunshot residue analysis)

17. Packaging • Each different item found at a crime scene must be placed in separate containers • Packaging evidence prevents damage as well as cross-contamination. • The evidence collector will have a large assortment of packaging materials and tools for any type of situation. • Forceps and similar tools may have to be used to pick up small items.

18. Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of trace evidence. • Manila envelopes, screw-cap glass vials, or cardboard pillboxes are also adequate for trace evidence. • Usually, mailing envelopes should not be use for evidence containers because powders and fine particles can leak from the corners.

19. 2 frequent finds at crime scenes require special attention: 1. Bloodstained materials- cannot be stored in air tight containers which can cause accumulation of moisture that encourages mold growth 2. Charred debris- must be stored in an airtight container to prevent evaporations of volatile petroleum residues.

20. Chain of Custody • Chain of Custody- a list of all persons who came into possession of an item of evidence. • Chain of custody must be established whenever evidence is presented in court as an exhibit.

21. Maintaining standard procedures in recording the location of evidence, marking it for identification, and properly completing evidence submission forms for lab analysis is critical to chain of custody. • Every person that handled or examined the evidence and where it is at all times must be accounted for.

23. Obtaining Reference Samples • Standard/Reference Sample-Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence. • The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires comparison with a known standard/reference sample. • It is important for the investigator to provide the crime lab with a thorough sampling of standard/reference materials.

24. Special Forensic Science Services • Forensic Pathology – involves the investigation of unnatural, unexplained, or violent deaths. • Forensic pathologists, along with medical examiners and coroners, are charged with determining cause of death. • The forensic pathologist may conduct an autopsy which is the medical examination of a body to determine cause of death.

25. After a human body expires, there are several stages of death: 1. Rigor mortis- results in the shortening of muscle tissue and the stiffening of body parts in the position at death (occurs within the first 24 hours and disappears within 36 hours) 2. Livor mortis- results in the settling of blood in areas of the body closest to the ground (begins immediately upon death and continues up to 12 hours) 3. Algor mortis- results in the loss of heat by a body (beginning about an hour after death, the body loses heat by 1 to1 ½ degrees F per hour until the body reaches the environmental temperature)

26. Forensic Anthropology- is concerned mostly with the identification and examination of human skeletal remains. • Forensic Entomology- is the study of insects and their relation to a criminal investigation, commonly used to estimate the time of death.