 Testimonial  Physical ◦ Direct/indirect ◦ Class/individual

 Direct Evidence: ◦ Needs no interpretation ◦ Testimonial evidence: testified to under oath ◦ Physical evidence: ie. DNA or Fingerprints

 Indirect evidence: ◦ Does not directly prove something ◦ Physical evidence: strand of hair, car LIKE yours

 Example:  Direct evidence: drugs on a person proves possession.

 Example:  Indirect evidence: wad of money on person….suspect drug sales.

 Testimonial evidence: ◦ Testified to under oath (usually in the court) ◦ Studies show 80% conviction rate in cases with eyewitness. ◦ Most known cases of wrongful conviction involved an eye witness.

 Things that diminish accuracy of eye witness: ◦ Brevity of encounter ◦ Darkness/ distance ◦ Stress: weapon diverts attention ◦ Time between event and questioning ◦ New info. Can effect memory  Read about case  Look at mug shots  Leading questions

 Studies show:  Witness more accurate at noting suspects: sex hair color Witness less accurate with noting suspects: age, height, specific race

 Witness is more accurate if suspect is  Similar to witness

 Make good witnesses: middle age  Make poor witnesses: ◦ Elderly ◦ Young children ◦ Alcohol or drug users ◦ Head injury

 Physical evidence: ◦ Can be direct or indirect ◦ Any object or material:  Microscopic: DNA, particles in soil  Macroscopic: hair, finger print, blood  odor

Physical Evidence can be used to: Prove a crime was committed; gas at fire Link suspect to crime scene; prints at scene I.D. people that were there Reconstruct scene

 Exemplar: the known or control group  Unknown: found at crime scene.  Example: find fingerprint at crime scene, compare it with all KNOWN prints through afis.

 Individual Evidence: evidence that can be traced to 1 source. Ex; DNA, fingerprints, broken glass or paper that fits like puzzle.  Class Evidence: can be classified into a group. Ex; black hair, white shirt, denim pants

 Does class evidence have any value?  What kind of evidence is most common?  Are most criminals smart?

 Classes of objects can be progressively narrowed by looking at successively more traits  Results in continually fewer objects being classified as similar to each other  If the traits being compared are not unique to the source ◦ item will possess traits that might be shared with a wide variety of sources

 Cocaine in a container can be identified as cocaine by its chemical properties  These properties are shared by all samples of the same molecular structure

 Cocaine from Columbia looks just like cocaine from any commercial source  Sometimes (particularly in drug cases) identification of the evidence item is all that is required  The source of the cocaine is not important ◦ its possession is illegal

 White cotton fibers are so common that they will be present in almost all trace evidence collection  Fiber can be identified as cotton via polarizing light microscope

 Origin from a specific source can’t be determined without looking at some non- cotton characteristic such as trace elements  Discovery of fibers that fall into the class of white cotton not very useful

 A bullet can be identified as.22 caliber by measurement  May be isolated to a specific manufacturer by its markings

 Manufacture usually produces millions of rounds of such ammunition ◦ can’t distinguish one round from another by looking only at caliber  Firearms examiner would look at individualizing characteristic such as bullet striae to increase the probative value

 The product rule:  The more class evidence you have the useful it becomes.

 The worth/value of evidence in court  Example….soil or red paint on jeans not very valuable…..both on 1 pair of jeans and both match soil/paint at crime scene!

 Product rule for the probative value of class evidence.  Suspect wearing white shirt, blue pants. Light brown hair

 How many kids in this class wearing white shirt  Say 10/30 =.333  Whole school population 1200  1200 x.333 = 400 kids in school wearing white shirt.

 Blue pants  Say 15/30 in this class =.5 .5 x 1200 = 600 in the school wearing blue pants

 Light brown hair 15/30 =.5 .5 x1200 = 600 students in school with light brown hair

 How do you estimate how many kids in the Whole school are wearing white shirts and blue pants and light brown hair

.333 (1/3) of kids in this class are wearing white shirts. .5 (1/2) of kids in this class are wearing blue pants .5 (1/2) of kids in this class have light brown hair

.333 x.5 x.5 =.0825 .0825 x 1200 = 100  Narrowed school population down to 100 possible suspects with all 3 criteria