The Crime Scene Where Forensic Science Learning Objectives

The Crime Scene Where Forensic Science

Learning Objectives 1) Define physical evidence 2) Discuss the responsibilities of the first police officer who arrives at the crime scene 3) Explain the steps to be taken to thoroughly record the crime scene 4) Describe proper procedures for conducting a systematic search of a crime scene for physical evidence 5) Describe proper techniques for packaging common types of physical evidence 6) Define and understand the concept of “chain of custody” 7) Relate what steps are typically required to maintain appropriate health and safety standards at the crime scene

Processing the Crime Scene – Crime labs run on physical evidence • Any object that can establish that a crime has or has not been committed or can link a crime and its victim or its perpetrator – If physical evidence is to be used effectively for aiding the investigator, its presence first must be recognized at the

Secure and Isolate the Crime Scene • Responsibility of the first officer arriving at the crime scene – Every individual who enters the scene is a potential destroyer of physical evidence • Locard Exchange Principle: Edmond Locard believed that when a criminal came in contact with an object or person, a cross-transfer of evidence occurred; every criminal can be connected to a crime by particles carried from the crime scene.

Secure and Isolate the Crime Scene • Special note should be taken of any people or vehicles leaving the scene • First priority is given to obtaining medical assistance for individuals in need of it and to arresting the perpetrator • As soon as it is possible, extensive efforts must be made to exclude all unauthorized personnel from the scene – At the same time, officers should detain all potential suspects or witnesses still at the scene

Evaluate the Area Once the scene is secured, the lead investigator will start the process of evaluating the area: – The boundaries of the scene are determined – The perpetrator’s path of entry/exit are established – Obvious items of evidence documented and photographed Initial Walk Through – helps the investigator gain an overview of the situation and develop a strategy for systematically examining and documenting the entire crime scene

Record the Scene • Investigators will only have a limited amount of time to work a crime scene in its untouched state • The opportunity to permanently record the scene in its original state must not be lost • Recording of the crime scene becomes a critical piece to the investigation process

Three Methods of Crime Scene Recording Photography Sketches Notes

Photography • Unaltered scene • Photographed from all necessary angles • Photos should include the area in which the crime actually took place and all adjacent areas • Overview photographs of the entire scene and surrounding area, including points of entry and exit Items of physical evidence are photographed to show their position and location relative to the entire scene – When size is important, a ruler or other measuring scale placed near object

Photography If scene includes a body: • Include position and location of body in relation to entire scene • Close-ups of injuries and weapons near body • After the body is removed, the surface beneath the body should be photographed

Photography Film vs. Digital – Is film best? – Digital photos can be easily manipulated using computer software. – Many jurisdictions have strict protocols for image security and chain of custody. Videotaping or digital video are more popular because costs have decreased. Advantages • Play back to check for completeness • Some video cameras take still pictures and have “night vision” • May be able to make stills from video Disadvantages • Camera will always shake • Zooming and panning can be sloppy • Extra noise can obscure narration • If still images are taken usually poor quality The still photograph remains unsurpassed in the definition and detail it provides the human eye!

Sketches Once photographs are taken, the crime-scene investigator will sketch the scene. Rough Sketch — a draft representation of all essential information and measurements at a crime scene. This sketch is drawn at the crime scene. It shows all recovered items of physical evidence, as well as other important features of the crime scene. Finished Sketch — a precise rendering of the crime scene, usually drawn to scale. This type is not normally completed at the crime scene. • Unlike the rough sketch, the finished sketch is drawn with care and concern for aesthetic appearance

Rough Sketch & Finished Sketch

Diagram of a Crime Scene

Measurements: Crime Scene Sketch • Triangulation: Two fixed points (A & B) in a scene are selected and the distance between them measured. The distance to the evidence (x & y) in the scene from each of these two points is measured. • Baseline: Points X and Y are fixed. Evidence a and b are measured along the a XY line and at right angles to XY. X b Y

Measurements at Crime Scene • http: //www. mathatube. com/measurementreading-a-ruler-starderd-unite. html

Crime Scene Sketch • https: //www. youtube. com/watch? v=hk. HGrdjft. A

Rectangular Coordinates

Station Line/ baseline Measurement

Triangulation

Illustrating the Sketch • Do not attempt to draw an object as it appears. Use symbols instead. • Use lettered or numbered squares, circles, figures, or points to represent various objects in the sketch. Explain in the diagram key what these objects represent. • If photography markers are used, ensure they correspond to same objects in the sketch. For example, if photo marker #5 is used to mark a handgun, make sure the handgun in the sketch is labeled #5. • Label all doors and windows. Show with a curved line which way the door swings. • Use an arrow to show the direction of the stairway. • Unnecessary height or length may be cut off with jagged lines. • Show measurements with dashed lines

Making a Crime Scene Sketch Legend • • Case number Type of crime Investigator Persons assisting Direction of North Identifying information in sketch (Key) Scale

• Note taking must be a constant activity throughout the processing of the crime scene. • These notes must include a detailed written description of the scene with the location of items of physical evidence recovered. • They must identify: – the time an item of physical evidence was discovered – by whom it was discovered – how and by whom it was packaged and marked – the disposition of the item after it was collected • The note taker has to keep in mind that this written record Notes http: //www. videojug. com/interv iew/documenting-a-crime-scene -2

The Search for Evidence • The search for physical evidence at a crime scene must be thorough and systematic. • The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search. • Failure can lead to accusations of negligence or accusations that evidence was “covered up” • For a factual, unbiased reconstruction of the crime, the investigator—relying upon his or her training and experience —must not overlook any pertinent evidence. • Physical evidence can be anything from massive objects to microscopic traces.

Search Methods

Search for Evidence • What to search for will be determined by the particular circumstances of the crime. – Homicide Case • The search is centered on the weapon and any type of evidence left as a result of contact between the victim and the assailant – Vehicle Case • In a hit and run case, the outside and undercarriage of the car must be examined with care

Beyond the Crime Scene • The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim. • Here, the medical examiner or coroner will carefully examine the victim to establish a cause and manner of death. • As a matter of routine, tissues and organs will be retained for pathological and toxicological examination. • At the same time, arrangements must be made between the examiner and investigator to secure a variety of items that may be obtainable from the body for laboratory examination.

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

• Collecting and Packaging Evidence A well-prepared evidence collector will arrive at a crime scene with a large assortment of packaging materials and tools ready to encounter any type of situation. • Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately

Collecting and Packaging Evidence • Forceps and similar tools may have to be used to pick up small items. • Unbreakable plastic pill bottles with pressure lids are excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence. • Alternatively, manila envelopes, screw-cap glass vials, or cardboard pillboxes are adequate containers for most trace evidence encountered at crime sites. • Ordinary mailing envelopes should not be used as evidence containers because powders and fine particles will leak out of their corners.

• Collecting and Packaging Evidence Small amounts of trace evidence can also be conveniently packaged in a carefully folded paper, using what is known as a “druggist fold. ” • Although pill bottles, vials, pillboxes, or manila envelopes are good universal containers for most trace evidence, two frequent finds at crime scenes warrant special attention. – If bloodstained materials are stored in airtight containers, the accumulation of moisture may encourage the growth of mold, which can destroy the evidential value of blood. – In these instances, wrapping paper, manila envelopes, or paper bags are recommended packaging materials. • Charred debris from a fire scene must be stored in an airtight container to prevent the evaporation of volatile petroleum residues

Druggist Fold

Maintaining a Chain of Custody: a list of all people who came into possession of an item of evidence. – Must be established whenever evidence is presented in court as an exhibit – Every person who handled or examined evidence must be accounted for – A minimum record would show the collector’s initials, location of the evidence, and date of collection • If the evidence is turned over to another individual this transfer must be recorded (each turn over must be recorded) – Frequently, all of the individuals involved in the collection and transportation of the evidence may be requested to testify in court *To avoid confusion and to retain complete control of the evidence at all times, the chain of custody should be kept to a minimum

Obtaining Standard/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 • May be gathered from a victim, suspect, or other sources – Ex: removal of control paint recovered at the scene of a hit-and-run **The quality and quantity of control specimens often determine the evidential value of crime-scene evidence – these control specimens must be collected, packaged, and treated with equal care

Submitting Evidence to Laboratory *evidence is usually submitted by personal delivery or by mail shipment *postal regulations do restrict the shipment of certain chemicals and live ammunition and prohibit the mailing of explosives Most laboratories require that an evidence submission form accompany all evidence submitted.

Processing A Crime Scene • https: //www. youtube. com/watch? v=ur 1 Gx. XZ Gn. NI • https: //www. youtube. com/watch? v=Wo. VO 4 s. AJI 4

Ensuring Crime-Scene Safety • The increasing spread of AIDS and hepatitis B has sensitized the law enforcement community to the potential health hazards that can exist at crime scenes. • In reality, law enforcement officers have an extremely small chance of contracting AIDS or hepatitis at the crime scene. • The International Association for Identification Safety Committee has proposed guidelines to protect investigators at crime scenes containing potentially infectious materials that should be adhered to at all times. (see pages

Legal Considerations at the Crime Scene Search Warrant! Removal of any evidence from a person or from the scene of a crime must be done in conformity with the Fourth Amendment or it will not be admissible

Legal Considerations at the Crime Scene Allowances for a warrantless search: 1) the existence of emergency circumstances 2) the need to prevent the immediate loss or destruction of evidence 3) a search of a person or property within the immediate control of the person provided it is made incident to a lawful arrest 4) a search made by consent of the parties involved OBTAIN A SEARCH WARRANT BEFORE INVESTIGATING AND COLLECTIN PHYSICAL EVIDENCE! (see Mincey vs. Arizona & Michigan vs. Tyler on page 47).