Crime Scene Basics

The Crime SceneThe Crime Scene• Crime Scene- any physical location in which a

crime has occurred or is suspected of having occurred– Classifications: scenes are combination or adaptation

of• Site of crime

– Primary Crime Scene- The original location of a crime or accident– Secondary Crime Scene- An alternate location where additional

evidence may be found• Size

– Macroscopic Crime Scene- composed of many crime scenes» Example:

– Microscopic Crime Scene- focused on specific types of physical evidence found @ Ma. C. S. » Example:

The Crime Scene (cont….)• Type of crime

– Examples: homicide, robbery, sexual assault, etc….

• Crime scene condition– Organized – Disorganized

• Location– Example: indoors, outdoors, vehicle, etc….

• Type of criminal behavior– Passive– Active

Crime Scene Personnel• Police Officers- 1st to arrive; secure scene; detain

persons of interest in crime

• Detectives- interview witnesses; consult with CSI; investigate crime using witness & evidence leads

• CSI/FSU Unit- documents details of C.S.; collects physical evidence; may be police or civilian

Crime Personnel (cont…)• District Attorney- obtains search warrants;

decides to prosecute

• Medical Examiner/Coroner/Death Investigator- decides to perform autopsy; preliminary causes of death @ scene

• Specialists- may be used for expert analysis for evidence (i.e. forensic entomologist)

The CriminalThe Criminal

• Suspect- person thought to be capable of committing a crime

• Accomplice- person associated with someone suspected of committing a crime

• Alibi- statement of where a suspect was at the time of a crime

Testimonial evidence includes oral or written statements given to police as well as court testimony by people who witnessed an event.

Physical evidence refers to any material items that would be present at the crime scene, on the victims, or found in a suspect’s possession.

Trace evidence refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or skin cells.

Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm

What will evidence collected at a scene do for the investigation?

• May prove that a crime has been committed• Establish key elements of a crime• Link a suspect with a crime scene or a victim• Establish the identity of a victim or suspect• Corroborate verbal witness testimony • Exonerate the innocent. • Give detectives leads to work with in the case

Types of Evidence

Basis of Crime Scene Investigation• Crime scene investigation

objectives– Recognize, preserve, collect,

interpret, & reconstruct physical evidence

• Forensic laboratory– Examines physical evidence to

provide investigator with info about evidence to solve cases

Types of Info Obtained from Physical Evidence

• Information on the Corpus Delicti– Determination of essential facts of investigation – i.e. physical evidence, patterns o’ evidence, laboratory

evidence examinations

• Information on the Modus Operandi– Criminal’s method of operation– Criminals tend to have repetitive behaviour

• Proving or Disproving Witness Statements– Credibility of witnesses, victims, suspects– Physical evidence absence/presence = accuracy o’ statements

• Linkage of Persons, Scenes, & Objects

Victim Suspect

Physical Evidence

Object Crime

Scene

• Identification of Suspects– Recognition, identification,

individualization– Individualization = comparison

testing• AFIS- fingerprint • CODIS- DNA

• Identification of Unknown Substances– i.e. drugs, poisons, bacteria

• Reconstruction of a Crime– “how” a crime occurred

• Providing Investigating Leads– Direct vs. Indirect Information• Direct= • Indirect =

Steps to Scientific Examination of a Crime Scene