1. The Crime Scene
Chapter 2

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

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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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

17. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

27. 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

28. 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

29. 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.

30. 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

31. 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

32. 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

33. 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

34. 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.

35. 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

37. 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

38. 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.

39. 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.

40. 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.

41. 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.

42. 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.

43. 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.

44. 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.).

45. 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).

46. 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

47. 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.

48. 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