Evidence

2014-2015

Physical Evidence• Physical Evidence-any and all objects or material

that is relevant in a crime.– can establish that a crime has or has not been committed – can back up witness testimony or prove it false– can link a suspect to their victim– can link a person or persons to a crime scene– can help investigators reconstruct a crime– May directly prove guilt or may be circumstantial (only

imply guilt).– In order to be useful it must be collected, preserved and

properly analyzed by forensic experts

CSI Myth…

• Crime laboratories do not solve crimes yet only enhance the ability of investigators to solve crimes by providing them with data.

Types of EvidenceDirect vs Circumstantial (Indirect) Evidence

Direct Evidence

• Prove that some committed crime

• First hand observations such as …– Eyewitness Accounts or

Testimonial evidence• Generally considered less reliable

– Police Dashboard Cameras– Surveillance Cameras

• Confessions are also considered to be Direct Evidence

Circumstantial or Indirect Evidence

• Evidence that can be used to imply a fact yet does not directly prove it– Is generally physical evidence.– Provides a link between a

suspect and a crime Scene or victim.

– The more circumstantial evidence the greater weight it carries

Eyewitness Accounts

• Eyewitness Accounts by Victims or Witnesses• Eyewitness accounts vary considerably from person to

person• Eyewitness accounts can be unreliable and have led to

the imprisonment of many wrongfully convicted suspects

» INNOCENCE PROJECT – Project with aim to free wrongfully convicted

• 87% of all wrongful convictions were a result of flawed eyewitness testimony

What Effects Our Observations

• Our Brains do not pay attention to all information around us.• Perception- interpreting information received from our senses

– Perception is skewed by our emotions, state of mind, and prior experiences or knowledge

• Short term memory – lasts only a short period of time– A few minutes to 24 hrs

• Long term memory – what is transferred to our memory bank for long periods– Days, weeks, months and yrs

Our ability to observe and remember can be heightened in certain circumstances.

• Example- 911 Attack• Most people can remember exactly where they were

and what they did on this day.

Types of EvidenceClass vs Individual Evidence

Class

• Evidence that narrows the identity of a criminal down to a certain subgroup (classification) of people

• Does not narrow suspects down to a single suspect or criminal.

• Can exclude some suspects• Example- ABO Blood Type,

Rh+ / Rh – Blood Type, Shoe size ect…

Individual• Evidence that narrows the

identity of a criminal down to a single individual.– Examples–

• DNA• Fingerprints• Handwriting***• Some other physical evidence

– Fragments that fit together like a jigsaw puzzle

» Ransom note torn from a notepad

– Sometimes impressions

Which examples do you think could be individual evidence?

Classification of Evidence by Nature

Biological- originating from living things

—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacteria, fungi, botanical material

Chemical- can be analyzed for chemical composition

—fibers, glass, soil, gunpowder, metals, minerals, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer

Physical- a mark or impression that can be analyzed and compared

—fingerprints, footprints, shoeprints, handwriting, firearms, tire marks, toolmarks, typewriting

Miscellaneous

—laundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification

Types of EvidenceTrace Evidence

• Small but measurable amounts of physical or biological evidence found at a crime scene– Examples… write down a few

• Fiber from clothing• Broken glass fragments• Paint chips • fingerprints on glass• Soil on shoes or tracked into a home• Drop of blood on a T shirt• Hair on a brush• Pollen on clothing• Pet hair on clothes or rugs

Locard’s Exchange Principle

• There is always a cross transfer of evidence between a suspect and victim or crime scene

• exchange of trace materials/evidence may occur between two people or a person and their other environmental surroundings