Introduction to Forensic Science Crime Scene Investigation
Participation Question • Can you give an example of a type of physical evidence that would be unstable or hard to collect at a crime scene? Can you suggest a way to document that evidence for trial?
Goal of Crime Investigation • Find the guilty party. • Exonerate the innocent. • If the investigator doesn’t preserve the evidence or document that preservation correctly, the evidence isn’t useful in court. • Crime Laboratory can’t make the evidence make sense if it isn’t collected correctly.
Two Evidence Types • Testimonial evidence is given in the form of a statement under oath in response to questioning. • Physical evidence is anything used, left, removed, altered or contaminated during the commission of the crime, by either the victim(s) or suspect(s).
Physical Evidence • Cannot lie, forget, be mistaken when properly identified, collected and preserved. • Is demonstrable. • Is not dependent on the presence of witnesses. • Is, in some instances, the only way to establish the elements of the crime.
Two Types of Physical Evidence • Individual Characteristics. • A piece of evidence that is unique and can be identified to the exclusion of all others. • Fingerprints • DNA • Class Characteristics • Features shared by all members of a group or class • Footprints
ARISN • Approach. • Render medical aid. • Identify additional victims or witnesses. • Secure the scene and physical evidence. • Notifications made appropriately.
Approach • Drive carefully- Sirens and high speed can be risky. • Scan for suspicious things or persons. • Be alert to evidence, witnesses and victims. • Call for more help and don’t dismiss the help until the situation is clear.
Rendering Medical Aid • The most important issue is to save a human life or prevent additional injury. • If the crime scene becomes contaminated while rendering aid, that is a price that must be paid. • There aren’t hard and fast rules that can be applied- discretion must be used.
Identifying Witnesses/Victims • May need medical attention. • Witnesses identify suspects and locations of additional evidence. • Separate the witnesses so they don’t cross-contaminate stories. • Be observant if witnesses give identical stories- they may have collaborated before police arrived.
Secure the Scene • Establish a perimeter. • Yellow tape. • Barriers. • Close the door for indoor crimes. • Police officers. • Secure scene and evidence. • Check for exit strategy of the criminal and follow to check for additional evidence.
Secure the Scene • Crime Scene Log is used to document the investigation: • Who entered the scene • Who left the scene • Time In and Out • Reason for entry to the scene • Keep out unauthorized police or fire personnel.
Make Notifications • First Responders notify superiors. • Call in Crime Scene Specialists: • Photo Specialists • Medical Examiners • Crime Scene Units
Types of Scenes • Major Scenes • Homicides • Officer involved shootings • DUI casualties • Felonious assaults in which death could occur. • Cases with potential for a major investigation • Non-major or discretionary
Major Indoor Scenes: Observations and Notes • Time • Entrances and Exits • Doors • Open • Closed • Locked • Type of lock (e.g. deadbolt) • Forced
Major Indoor Scenes Cont.. • Windows • Open • Closed • Locked • Unlocked • Lights (on/off) • Odors • Cigarettes, cigars, perfume, alcohol, gas, gun powder, unusual odors.
Major Indoor Scenes Cont.. • Names of Persons at the scene, including emergency personnel. • Condition of the scene: • In disarray/good order • Furniture tossed about • Stains • Position of weapons
Major Indoor Scenes Cont.. • Avoid the following: • Do not touch inside doors, doors and door frames. • Do not move anything. • Do not smoke, or use the telephone, toilet, sink or ashtrays. • Beware where you stand and what you touch. Hold your hand behind your back while surveying the crime scene.
Outdoor Crime Scenes • Establish and protect a large perimeter, especially at parks, beaches or open areas. • If tire/footprint or other impression evidence is found, warn others to stay away. • Try to determine the suspect’s route of approach and escape. • Identify and protect evidence, then collect it. Some evidence is difficult to collect.
Secondary Crime Scenes • Evidence may be located some distance from the original crime scene: • Discarded clothing • Discarded weapons • Blood trails • Protect secondary crime scene evidence as well as primary crime scenes.
Death Cases • Four methods by which death can occur: • Natural Causes • Accidental Death • Suicide • Homicide • Medical Examiner makes this decision.
Death Cases • All death scenes should be treated like a homicide until the medical examiner declares otherwise. • First responders should not hesitate to ask for assistance if needed. Better to err on the side of caution. • Key to a successful investigation is documentation.
Death Cases • Make note of some of the following: • Believability of the witnesses. • Jittery, nervous, anxious to leave the scene? • Does their version of the incident seem questionable? • Condition of the scene. • History of the victim and/or suspect if known. • Preservation of notes or writing for later analysis. • Preserve medications and containers.
Documenting the Crime Scene • Investigators have only a limited amount of time to work a crime site in its untouched state. • Photographs, notes and diagrams document the condition of the crime site and to delineate the location of physical evidence. • Photographs, notes and diagrams prove useful during the subsequent investigation AND are also required for presentation at a trial often months or years later. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Documenting the Crime Scene • A lead investigator will start the process of evaluating the area before collecting evidence. • First, the boundaries of the scene must be determined. • This is followed by the establishment of the perpetrator’s path of entry and exit. • The investigator then proceeds with an initial walk-through of the scene to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Crime Scene Search • The crime scene coordinator may choose from a variety of crime scene search patterns based upon the type and size of the crime scene. • Key is to be orderly and thorough- don’t walk over too much but don’t miss anything. • Spiral • Strip/Line • Grid • Zone/Quadrant • Pie/Wheel
The Search • 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 evidence collectors. • Physical evidence can be anything from massive objects to microscopic traces. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Collecting Physical Evidence • Although much physical evidence is clearly visible, some may only be detected at the crime laboratory. • E.g. Semen on sheets after a sexual assault. • It is important to notice and collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernail scrapings, in addition to more obvious physical evidence. • Investigators need to keep from contaminating the evidence- e.g. their DNA or fibers.
The Victim Can Provide Evidence • The search for physical evidence must continue to the autopsy room of a deceased victim. • The medical examiner or coroner will carefully examine the victim to establish a cause and manner of death. • Tissues and organs will be retained for pathological and toxicological examination. • Also they will provide any physical evidence from the body of the victim. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Beyond The Crime Scene The following are often collected and sent to the forensic laboratory: • Victim’s clothing • Fingernail scrapings • Head and pubic hairs • Blood (for DNA typing purposes) • Vaginal, anal, and oral swabs (in sex related crimes) • Recovered bullets from the body • Hand swabs from shooting victims (for gunshot residue analysis) PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
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 other kinds of trace evidence. • Manila envelopes, screw-cap glass vials, or cardboard pillboxes are also good containers • Ordinary mailing envelopes should not be used because powders will leak out of their corners.
Packaging to Preserve Evidence • Each item or similar items collected at different locations must be placed in separate containers. • Packaging evidence separately prevents damage through contact and prevents cross-contamination. • The well-prepared evidence collector will have a large assortment of packaging materials and tools ready to encounter any type of situation. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Packaging • Trace evidence can also be packaged in a carefully folded paper, using a “druggist fold.” • 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. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
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. • Although most investigators have little difficulty recognizing and collecting relevant crime-scene evidence, few seem aware of the necessity and importance of providing the crime lab with a thorough sampling of standard/reference materials. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Evidence Recovery Log • A chronological record of who found what evidence, where, witnessed by whom, and notations about other ways the evidence may have been documented, e.g., photography
Evidence Recovery Log Records are critical for prosecution of the crime as well as records of unbroken chain of evidence.
Chain of Custody • Chain of Custody—A list of all persons who came into possession of an item of evidence. • The chain of custody, must be established whenever evidence is presented in court. • Adherence to standard procedures in recording its location, marking it for identification, and properly completing evidence submission forms for laboratory analysis is critical. • Every person who handled the evidence and where it was at all times must be documented. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Case Studies • O.J. Simpson • Evidence not handled well, leading it suggestions it was compromised by dishonest criminalists and police. • JonBenet Ramsey • Crime scene wasn’t secured and family friends and father found body, contaminating the scene.
Notes • Notes must include a detailed written description of the scene with the location of items of physical evidence recovered. • Notes 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 • This written record may be the only source of information for refreshing one’s memory! PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Visually Documenting the Crime Scene Is Critical • Video taping • Photographing • Sketching
Photography • The most important prerequisite for photographing a crime scene is for it to be in an unaltered condition. • Unless there are injured parties involved, objects must not be moved until they have been photographed from all necessary angles. • As items of physical evidence are discovered, they are photographed to show their position, size and location relative to the entire scene. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Photography • After overviews are taken, close-ups should be taken to record the details of the object itself. • A ruler or other measuring scale may be placed near the object and included in the photograph. • Once photographs are taken, the crime-scene investigator will sketch the scene. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Photography • Photograph the crime scene as soon as possible. • Prepare a photographic log that records all photographs and a description and location of evidence. • Establish a progression of overall, medium, and close-up views of the crime scene. • Photograph from eye level to represent the normal view.
Photography • Photograph the most fragile areas of the crime scene first. • Photograph all stages of the crime scene investigation, including discoveries. • Photograph the condition of evidence before recovery. • Photograph the evidence in detail and include a scale, the photographer's initials, and the date.
Photography • When a scale is used, first take a photograph without the scale. • Photograph the interior crime scene in an overall and overlapping series using a wide-angle lens. • Photograph the exterior crime scene, establishing the location of the scene by a series of overall photographs including a landmark. Photographs should have 360 degrees of coverage. Consider using aerial photography. • Photograph entrances and exits.
Photography • Photograph important evidence twice. • A medium-distance photograph that shows the evidence and its position to other evidence. • A close-up photograph that includes a scale and fills the frame. • Acquire prior photographs, blueprints, or maps of the scene.
Sketches • Rough Sketch—A representation of all essential information, evidence and measurements at a crime scene drawn at 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. PRENTICE HALL ©2007 Pearson Education, Inc. Upper Saddle River, NJ 07458 CRIMINALISTICS An Introduction to Forensic Science, 9/E By Richard Saferstein
Sketches can illustrate where evidence was collected Vandalia Science Education ©2007 Vandalia Research, Inc. Huntington, WV 25701
Crime Scene Safety • Potential health hazards exist at crime scenes. • Chemicals (e.g. methamphetamine production) are hazardous. • AIDS and hepatitis B and C are two possible blood born diseases that can be transmitted. • Law enforcement officers have a very 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. • Universal Precautions- assume all body fluids are contagious.