Crime Scene Processing Crime Scene Processing and Physical Evidence Outline • Define physical evidence • Crime scene security • Thorough searching and recording of the crime scene • Procedures used for conducting a systematic search of a crime scene for physical evidence • Proper techniques for packaging common types of physical evidence • Concept of chain of custody • Safety standards at the crime scene The Crime Scene • Physical Evidence: any and all objects which can determine whether crime has been committed or can provide a link between Crime, Victim, and the Suspect. • Locard Exchange Principle: Exchange of materials between two objects occurs whenever two objects come in contact with one another. – A person committing a crime will not only take traces of the crime scene away with him/her but will also leave traces of his/her presence behind at the crime scene. – Therefore the forensic science truly starts at the crime scene. – The items of physical evidence that are examined by forensic scientists are retrieved from the crime scene. Crime Scene Processing and Physical Evidence Outline • Define physical evidence • Crime scene security • Thorough searching and recording of the crime scene • Procedures used for conducting a systematic search of a crime scene for physical evidence • Proper techniques for packaging common types of physical evidence • Concept of chain of custody • Safety standards at the crime scene The Crime Scene • Crime Scene Security is very important: – The way in which the crime scene is secured, recorded and how all of the physical evidence is located, collected, packaged, labeled and stored are fundamental to the success of subsequent forensic analysis. • Preservation of the evidence is critical – In this presentation we will explore the principles, methods and procedures involved in the processing of a crime scene to collect all possible physical evidence related to a crime. Crime Scene Security Preservation of a crime scene. • The first officer(s) arriving on the scene is responsible to secure crime scene. • The other first priority of the officer is to obtaining medical assistance to individuals that may be injured or those that need immediate medical help and arrest the individual that has or may have perpetrated the crime. • As soon as it is humanly possible, the officer should make efforts to exclude all unauthorized personnel from the scene. • As the additional officers arrive, measures are immediately initiated to isolate the area. – Ropes or barricades along with the strategic positioning of guards will prevent unauthorized access to the area. • Once the scene has been secured, a lead investigator will start the process of evaluating the area. Crime Scene Processing and Physical Evidence Outline • Define physical evidence • Crime scene security • Crime scene examination and thorough searching and recording of the crime scene • Procedures used for conducting a systematic search of a crime scene for physical evidence • Proper techniques for packaging common types of physical evidence • Concept of chain of custody • Safety standards at the crime scene Crime Scene Team • • • • • Team leader Photographer and photographic log recorder Sketch preparer Evidence recorder/Custodian Evidence collection experts Crime Scene Processing and Physical Evidence Crime Scenes cannot be processed without a warrant • In the case of Mincey v. Arizona, the Supreme Court restricted the practice of conducting a warrentless search at a homicide scene. • In the case of Michigan v. Tyler, the Supreme Court dealt with search and seizure procedures at a fire scene. The Crime Scene Examination • To seek answers to a number of questions. – Who: • Who was the victim of the crime? • Who committed the crime? and • Who witnessed the crime? – When: • When was the crime committed? – Why: • Why did the crime happen where it did? • Why did the crime happen when it did? The Crime Scene Examination • Where: – Where did the key events that produced the crime scene take place? (For example, in the case of a body found in suspicious circumstances, there will be clues present that indicate whether the person died at the scene or somewhere else) – Where and how did the people involved in the crime enter and, if applicable, leave the scene? – Where were those people who were involved in the crime located at the time of its initiation, and were they standing, sitting, kneeling, etc. at that time? – Where did the objects involved in the incident originate from and where did they go to after the crime? The Crime Scene Examination • To seek answers to a number of questions. – What: – What was the sequence of events that occurred during the process of committing a crime? – What was the motive for committing the crime? – What was the modus operandi of the criminal(s) involved? (Modus operandi: The way in which the person committing the crime carries out the act). – What type of objects (tools, vehicles, weapons, etc.) was used to commit the crime? – What was left behind at the scene during the crime? – What was removed from the scene during the crime? Boston Marathon Bombing The Crime Scene Examination • To seek answers to a number of questions. – Why: • Why did the crime happen where it did? • Why did the crime happen when it did? Crime Scene Processing and Physical Evidence Outline • Define physical evidence • Crime scene security • Thorough recording of the crime scene • Procedures used for conducting a systematic search of a crime scene for physical evidence • Proper techniques for packaging common types of physical evidence • Concept of chain of custody • Safety standards at the crime scene Crime Scene Processing • To answer questions posed, it is necessary to: – Preserve the scene in the state in which it was found by restricting access to trained and authorized personnel only and, where necessary, protecting it from the elements. – Record the state in which the crime scene was found via • note taking, • photographing, • video recording, and sketching – Utilize the data to create a virtual scene(s) using computer graphics for better understanding of the crime scene and its investigation. – Construct a systematic log of all actions taken at the scene and by whom these actions were taken. – Systematically search and recover of physical evidence. – Package and label physical evidence. – Store physical evidence properly. – Request forensic examination (analysis) of physical evidence. Crime Scene processing • All crime scenes are different and the amount of time and effort required for processing a given crime scene will depend on a number of factors. – An assessment of the likely amount of useful evidence that can be collected from the crime scene, and – The priorities of the government and the police with regard to the type crime being investigated. • For example, serious crimes such as homicide or rape receive more attention than less serious crimes (volume or petty crime) such as car theft. • Further, within the area of volume or petty crimes, not all types of scene will necessarily be given the same priority. • Irrespective of the type of crime scene being examined, the optimum effectiveness of crime scene is achieved only when each of actions (outlined above) are carried out with due care, diligence and expertise. • The investigations should be ethical and follow legal procedures, e.g., to search the house of suspect, one should have a court order to do so. Crime Scene Processing • Other factors that are very significant during a crime scene investigation are as follows: 1. The initial assessment of the scene (type of crime). 2. The management of any risks to the health or safety of both investigators and the public. 3. The interpretation of the scene in the light of the evidence gathered. 4. The communication between all individuals involved in the investigation. 5. Assessment of the intelligence value of the information obtained from the crime scene. 6. Maintenance of integrity of physical evidence collected from the scene. 7. Preparation of reports and statements. 8. Presentation of evidence in court, where and when required. Recording the Scene • Investigators have only a limited amount of time to work a crime site in its untouched state. • The opportunity to permanently record the scene in its original state must not be lost. • Therefore recording the crime scene is critical • Recording is accomplished via: – Photography/Videography – Sketches – Notes Sketches (Rough and Finished) • Sketches: – Once photographs are taken, the crime-scene investigator should sketch the scene. – The investigator may not have skills or time to make a polished sketch of the scene. However, it is necessary to make a rough sketch containing an accurate depiction of the dimensions of the scene and showing the location of all objects • Finished sketch: – A sketch drawn with care and concern for aesthetic appearance – Prepared with the aid of templates and drafting tools by a skilled individual and is drawn to scale. – A finished sketch must reflect information contained within the rough sketch in order to be admissible evidence in a courtroom. – Computer-aided drafting (CAD) is more commonly used to draw such sketches. Crime Scene Sketch • Fold-down or crossprojection sketch: – Room is unfolded as if it is a cardboard box – Each wall is presented as a flap extending from the floor. Sketches (Rough and Finished) • Finished sketch: – A sketch drawn with care and concern for aesthetic appearance – Prepared with the aid of templates and drafting tools by a skilled individual and is drawn to scale. – A finished sketch must reflect information contained within the rough sketch in order to be admissible evidence in a courtroom. – Computer-aided drafting (CAD) is more commonly used to draw such sketches. Photography • Provides an unaltered record of the scene. • Unless there are injured parties involved, objects must not be moved until they have been photographed from all angles. • Overview photographs: entire scene and surrounding area, including points of exit and entry, must be included. • As items of physical evidence are discovered, they are photographed to show their position and location relative to the entire scene. • After the overviews, close-ups should be taken to record the details of the objects. • When the size of an item is of significance, a ruler may be inserted near the object and included in the photograph as a point of reference. • Use of videotape at crime scenes is becoming increasingly popular. • The same principles used in crime-scene photographs apply to videotaping. Notes • 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 also identify the time an item of physical evidence was discovered, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collected. • Tape-recording notes at a scene can be advantageous-detailed notes can be taped much faster than they can be written. • Another method of recording notes is by narrating a videotape of the crime scene. Searching the Crime Scene • The search for physical evidence at a crime scene must be thorough and systematic. When looking for an object that is suspected to be a specific distance When most thorough search is needed When searching a large area looking for a large objects Large crime scenes with multiple evidence collectors • The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search. Crime Scene Processing and Physical Evidence Outline • Define physical evidence • Crime scene security • Thorough recording of the crime scene • Procedures used for conducting a systematic search of a crime scene for physical evidence • Proper techniques for packaging common types of physical evidence • Concept of chain of custody • Safety standards at the crime scene Packaging Evidence • Each different or similar item of physical evidence collected at different locations must be placed in separate appropriate containers. • Packaging each evidentiary item separately is important from the viewpoint of preventing damage through contact and preventing crosscontamination between items. Chain of Custody and Collection of controls • Chain of Custody – During the collection of evidence, the chain of custody - a record for denoting the location of the evidence, must be maintained. • Collection of controls – In addition, proper controls, such as hairs, blood, and fibers, must be collected at the crime scene and from appropriate subjects for comparison purposes in the laboratory.
