Crime Scene Basics

The 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 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- 1 st 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 scene Specialists- may be used for expert analysis for evidence (i.e. forensic entomologist)

The 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: 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 VictimSuspect Physical Evidence ObjectCrime 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 Recognition Scene Survey Documentation Collection & Preservation Identification Comparison Testing Individualization Evaluation Interpretation Reconstruction Reporting & Presentation