Forensic Science

CRIME SCENE: Any physical location in which a crime has occurred or is suspected of having occurred.

PRIMARY CRIME SCENE: The original location of a crime or accident.

SECONDARY CRIME SCENE: An alternate location where additional evidence may be found.

ALIBI: Statement of where a suspect was at the time of a crime.

ACCOMPLICE: Person associated with someone suspected of committing a crime.

SUSPECT: Person thought to be capable of committing a crime.

Crime Scene Vocabulary

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.

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

What evidence can be found at a crime scene? Brainstorm with your group to come up with a list of evidence you would collect from this crime scene.

POLICE OFFICERS are typically the first to arrive at a crime scene. They are responsible for securing the scene so no evidence is destroyed and detaining persons of interest in the crime.

SCENES OF CRIME OFFICERS document the crime scene in detail and are usually skilled photographers trained in lifting finger prints and foot/tire impressions – usually collect physical evidence for less serious crimes.

THE CRIMINAL IDENTIFICATION OFFICER – searches crime scene; finds, gathers and analyzes evidence then if needed sends evidence to labs for necessary analysis

The REGIONAL CORONER (if a homicide) may or may not be present to determine a preliminary cause of death.

SPECIALISTS (entomologists, forensic scientists, forensic psychologists) may be called in if the evidence requires expert analysis.

CRIMINAL INVESTIGATIONS BUREAU OFFICER is the detective who interviews witnesses and consults with the CSI unit. They investigate crimes by following leads provided by witnesses and physical evidence; they also interrogate and eventually arrest suspects.

Crime Scene Personnel

Step 1: InterviewThe first step in investigating a crime scene is to interview the first officer at the scene or the

victim to determine what allegedly happened, what crime took place, and how the crime was committed. This information may not be factual information but it will give the investigators a place to start.

Step 2: ExamineThe second step in the investigation of a crime scene, which will help identify possible

evidence, identify the point of entry and point of exit, and outline the general layout of the crime scene.

Step 3: DocumentThe third step in the protocol involves creating a photographic record of the scene as well as a

rough crime scene sketch to demonstrate the layout of the crime scene and to identify the exact position of the deceased victim or other evidence within the crime scene.

Step 4: ProcessThis is the last step in the protocol. The crime scene technician will process the crime scene

for evidence, both physical and testimonial evidence. It is the crime scene technician’s responsibility to identify, evaluate and collect physical evidence from the crime scene for further analysis by a crime laboratory.

Crime Scene Protocol

Drug Chemistry – Determines the presence of controlled substances and the identification of marijuana.

Trace Chemistry - Identification and comparison of materials from fires, explosions, paints, and glass.

Microscopy – Microscopic identification and comparison of evidence, such as hairs, fibers, woods, soils, building materials, insulation and other materials.

Biology/DNA – Analysis of body fluids and dried stains such as blood, semen, and saliva.

Toxicology – Tests body fluids and tissues to determine the presence of drugs and poisons.

Latent Prints - Identification and comparison of fingerprints or other hidden impressions from sources like feet, shoes, ears, lips or the tread on vehicle tires.

Ballistics (Firearms) – Study of bullets and ammunition through the comparison of markings on fired bullets, cartridges, guns, and gunpowder patterns on people and objects.

Toolmarks – Examines marks left by tools on objects at a crime scene or on a victim, such as a hammer used to break a door or a screwdriver used to pick a lock.

Questioned Documents - Examination of documents to compare handwriting, ink, paper, writing instruments, printers, and other characteristics that would help to identify its origin.

Investigating the Evidence Forensic Science disciplines at many major Crime Labs include the following:

Chain of Custody

• Testimony and documentation that details the location and condition of evidence from seizure to trial.

• It assures the court that items entered into evidence are in the same condition as when they were seized.

• The chain of custody and the procedures used to analyze evidence are more often challenged than the science behind the analysis.

“FORENSIC”

• FROM LATIN

• “FORENSIS” OR “FORUM”

• In other words, “COURT”

• “Forensic” is an adjective meaning:

“related to court.”

DIRECT EVIDENCE

VS.

CIRCUMSTANTIAL EVIDENCE

DIRECT EVIDENCE

VS.

CIRCUMSTANTIAL EVIDENCE

• Which is stronger according to the law?

• NEITHER• “The law treats both equally. Neither is necessarily better

or worse than the other” (Standard Jury Instructions)

• Which is stronger in reality?

•CIRCUMSTANTIAL

•NO DOUBT ABOUT IT

DIRECT vs CIRCUMSTANTIAL

Locard’s Exchange Principle “Wherever he steps, whatever he touches, whatever he leaves, even

unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value.” – Professor Edmond Locard (1877-1966)

On the Negative SideUltimately, forensic analysis is still dependent upon human interpretation; the results of forensic testing must still be interpreted by a person and thus can be misinterpreted.

IS DNASTRONGEVIDENCE?

ABSOLUTELY

WHAT TYPE OF EVIDENCE IS D.N.A.?

CIRCUMSTANTIAL

IS “DIRECT EVIDENCE”

(EYEWITNESS EVIDENCE) STRONG?

In the past, there have been miscarriages of justice, persons have been wrongly convicted, because eyewitnesses have made mistakes.

It is quite possible for an honest witness to make a mistake in identification. Honest people do make mistakes. An apparently convincing witness can be mistaken. So can a number of apparently convincing witnesses.

STANDARD

JURY

INSTRUCTIONS

FORENSIC EVIDENCE IS VERY IMPORTANT(LIKE ALL CIRCUMSTANTIAL EVIDENCE)

* PREVENTING MISCARRIAGES OF JUSTICES* FINDING THE PROPER PERPETRATOR* EXCLUDING THE INNOCENT* PROVING THE CASE IN COURT

FORENSIC EVIDENCE’S ROLE IS REALLY TO PROVIDE NEW AREAS OF CIRCUMSTANTIAL EVIDENCE WHICH:

•CONFIRMS IDENTIFICATION EVIDENCE

- and -

•CAN PROVE A CASE ON ITS OWN (EVEN WHERE THERE IS NO DIRECT EVIDENCE)

•WE HAVE ALWAYS HAD CIRCUMSTANTIAL EVIDENCE

•CIRCUMSTANTIAL EVIDENCE HAS ALWAYS BEEN HUGE

•FORENSICS HAS SIMPLY BROKEN WIDE OPEN THE WORLD OF CIRCUMSTANTIAL EVIDENCE

•THE FORENSIC IDENTIFICATION SERVICE GIVES US CELL PHONE RECORDS

• GREAT EVIDENCE• WHO CALLED WHOM• AND WHERE THEY WERE• BUT NOT FORENSIC SCIENCE

THE BOTTOM LINE•CIRCUMSTANTIAL EVIDENCE IS THE KEY TO MOST CRIMINAL CASES.

•CIRCUMSTANTIAL EVIDENCE HAS BEEN AROUND FOREVER.

•FORENSIC EVIDENCE, AT ITS CORE, IS JUST A POWERFUL NEW ASSORTMENT OF CIRCUMSTANTIAL EVIDENCE.