The Crime Scene Chapter 2

Physical Evidence Encompasses any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator Valuable only when its collection is performed correctly

Physical Evidence Crime labs DO NOT solve crimes– they just analyze the evidence Investigators solve crimes

Crime Scenes It is the beginning point for obtaining evidence which will be used by the crime scene investigator and the forensic expert A thorough investigation of the crime scene must be completed

Defining a Crime Scene Crime scenes are never consistent- they are ALWAYS inconsistent Each one presents an investigator with a new challenge Can be classified by the location of the crime Primary crime scene Secondary crime scene

Defining a Crime Scene Crime scenes may also be classified according to size Macroscopic Comprised of many crime scenes Gunshot an victim’s body dumped in field Microscopic Trace evidence found on the body, gunshot residue, or tire tread marks

Defining a Crime Scene Also classified by Type of crime Homicide, robbery, burglary, sexual assault By organization or disorganization of scene Physical location Indoor, outside, vehicle Criminal behavior associated with scene Passive or active

Crime Scene Investigation Based on the scientific method and the Locard Exchange Principle, logic and forensic techniques involve Recognition- scene survey, documentation, collection Identification- comparison testing Individualization- evaluation and interpretation Reconstruction- reporting and presenting

Crime Scene Investigation Goals are to determine the following What happened Where did it happen When did it happen Why did it happen Who may have perpetrated these actions How was the incident carried out

Processing a Crime Scene 8 universal rules exist Safety first Secure and protect the scene Fulfill the basic legal requirements Photograph the scene Identify and mark evidence Collect, label, and package evidence Diagram the scene Write a report

The Crime Scene The first officer at the crime scene is responsible for securing and protecting the area Must first make sure that if the victim is alive, medics are on their way Must secure the area with crime scene tape or other barriers Must make sure that the evidence does not get compromised Must make sure that witnesses do not leave the crime scene

First Responders must protect the scene Every individual who enters the scene has the potential to destroy physical evidence, even if by unintentional carelessness. To exercise proper control over the crime scene, the officer protecting it must have the authority to exclude everyone, including fellow police officers not directly involved in processing the site or in conducting the investigation.

The Crime Scene Investigator Has only a limited amount of time to work a crime scene Must photograph the crime scene Must sketch the crime scene Must take notes Must collect, document, and package evidence

Photography The crime scene must not be altered Objects must remain where they are until photographed Any proof that the crime scene was compromised would cause the evidence to not be admissible in court If evidence has been removed or moved, it must be mentioned in the report

Photography Each crime scene needs to be photographed as completely as possible All areas where the crime took place should be photographed at different angles Entries and exits must also be photographed at different angles It is important to have close-up shots and far-away shots Evidence should be photographed with a ruler as a point of reference

Sketches After photographs are taken, the investigator will sketch the crime scene 2 types of sketches exist Rough- a draft representation of all essential info and measurements at a crime scene Finished- a precise rendering of the crime scene All sketches are drawn to scale All sketches have a legend showing where certain items are at the crime scene

Sketches Crime scene sketches require Title or caption Legend of abbreviations Symbols Numbers of letters used Compass designation Scale, if drawn to scale Documentation block with case number, offense type, victim’s names, location, date and time, and sketcher’s name

Notes Must be taken throughout processing the crime Should include Date and time of notification and information received Arrival information Scene description Victim description Crime scene team members

Notes Must also include a detailed written description of the scene with the location of items of physical evidence recovered Must also identify the time an evidence was discovered, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collected

Infuential factors How one conducts a crimescene search will depend on the 1. locale and 2. size of the area, as well as on the 3. actions of the suspect(s) and victim(s) at the scene

Search for Evidence Must be thorough and systematic Must make sure not to overlook any pertinent evidence Failure to do so can lead to accusations of negligence or of covering up the evidence

Search for Evidence Field evidence technician responsible for conducting search for evidence May also photograph the crime scene Looks for fingerprints, footprints, tool marks, hairs, fibers, etc Must also collect possible carriers of trace evidence

Search for Evidence Crime scene is usually searched in segments 4 types of segments exist Spiral search method- Search starts at an outer point and gradually moves toward the center Grid method- Crime scene divided into a grid and each grid segment is searched Strip or line search- Crime scene divided into strips and each strip is searched Quadrant or zone search- Crime scene divided into quadrants and each quadrant is searched

Search for Evidence Evidence must also be collected from the body (if victim died) by the medical examiner Evidence needed includes Victim’s clothing Fingernail scrapings Head and pubic hairs Blood Vaginal, anal, and oral swabs (sex crimes) Recovered bullets from the body Hand swabs from shooting victims

Collecting and Packaging Evidence Physical evidence must be handled and processed in a way that prevents any change from taking place between the time it is removed from the crime scene and the time it is received by the crime laboratory

Integrity The integrity of evidence is best maintained when the item is kept in its original condition as found at the crime site. Whenever possible, evidence should be submitted to the laboratory intact. Blood, hairs, fibers, soil particles, and other types of trace evidence should not normally be removed from garments, weapons, or other articles that bear them. Instead, the entire object should be sent to the laboratory for processing.

Collecting and Packaging Evidence Each different item or similar items collected at different locations must be placed in separate containers Prevents damage through contact and prevents cross- contamination Forceps and other similar tools may have to be used to pick up small items

Collecting and Packaging Evidence Small items may be put in unbreakable plastic pill bottles with pressure lids Great for hairs, glass, fibers, and other small or trace evidence Manila envelopes are also good containers for evidence Paper bags are excellent containers for large evidence Mailing envelopes should NEVER be used to hold evidence

Collecting and Packaging Evidence Any evidence that is wet must be air dried before being placed in a container Bloodstained evidence should never be stored in an air-tight container Could cause mold growth which damages the evidence

Collecting and Packaging Evidence After evidence is collected and packaged, the container it is in must be marked and sealed Most items should be packaged in a primary container and then placed in a secondary container Hair is placed in a vial which is then placed inside a paper bag

Druggist Fold Small amounts of trace evidence can also be conveniently packaged in a carefully folded paper, using what is known as a “druggist fold.” This consists of folding one end of the paper over one-third, then folding the other end (one-third) over that, and repeating the process from the other two sides. After the paper is folded in this manner, the outside two edges are tucked into each other to produce a closed container that keeps the specimen from falling out.

Chain of Custody Is a list of all persons who come in possession of an item of evidence Must be established whenever evidence is presented in court The evidence container must be marked for identification The collector’s initials should be placed on the seal If evidence is turned over to another person, the transfer must be recorded

Obtaining Reference Samples A standard/reference point is physical evidence whose origin is known, such as hair from a suspect that can be compared to a hair found at the crime scene Exists with blood, glass, soil, fibers, paint chips, etc

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.

Obtaining Reference Samples 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.

Substrate Controls These are materials close to areas where physical evidence has been deposited. For example, substrate controls are normally collected at arson scenes. If an investigator suspects that a particular surface has been exposed to gasoline or some other accelerant, the investigator should also collect a piece of the same surface material that is believed not to have been exposed to the accelerant.

Substrate controls example Another common example of a substrate control is a material on which a bloodstain has been deposited. Unstained areas close to the stain may be sampled to determine whether this material can interfere with the interpretation of laboratory results. Thorough collection and proper packaging of standard/reference specimens and substrate controls are the mark of a skilled investigator.

Special Forensic Science Services Forensic Pathology involves the investigation of unnatural, unexplained, or violent deaths. Forensic pathologists in their role as medical examiners or coroners are charged with determining cause of death.

Special Forensic Science Services The forensic pathologist may conduct an autopsy which is the medical dissection and examination of a body in order to determine the cause of death. Autopsies are generally performed if the death is deemed suspicious.

Special Forensic Science Services After a human body expires there are several stages of death. 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 hrs. and disappears within 36 hrs.).

Special Forensic Science Services Livor mortis results in the settling of blood in areas of the body closest to the ground (begins immediately on death and continues up to 12 hrs.). Algor mortis results in the loss of heat by a body (a general rule, beginning about an hour after death, the body loses heat by 1 to 1 1/2 degrees Fahrenheit per hour until the body reaches the environmental temperature).

Special Forensic Science Services Forensic Anthropology is concerned primarily with the identification and examination of human skeletal remains. Identification is done by examining bones that may identify race or sex or injury or they may create a facial reconstruction Courtesy of C. Fanning

Special Forensic Science Services Forensic Entomology is the study of insects and their relation to a criminal investigation, commonly used to estimate the time of death.

Forensic Entomology These determinations are not always straightforward, however. The time required for stage development is affected by environmental influences such as geographical location, climate, and weather conditions. For example, cold temperatures hinder the development of fly eggs into adult flies. The forensic entomologist must consider these conditions when estimating the postmortem interval. Knowledge of insects, their life cycles, and their habits make entomological evidence an invaluable tool for an investigation