Week 4 - evidence

what is evidence

information

Trier of fact

whoever decides guilt or innocence in a legal case ( e.g. judge, jury)

what is physical evidence

generated as a part of the crime and recovered at the scene

demonstrative evidence

some evidence is created to augment or explain real evidence

circumstantial / presumptive evidence

evidence based on inference, not personal knowledge/observation

probative evidence

tends to prove or disprove a point in issue

Transient Evidence

things that cant be collected/ taken back to a lab

Pattern Evidence

a patter/imprint that is left behind, could possibly be matched

conditional evidence

evidence that exists as a result of the crime

transfer evidence

evidence left behind due to some sort of exchange between surfaces/objects

examples of physical evidence

hair, bodily fluids, clothing, fingerprints, paint

examples of demonstrative evidence

graphs, charts, reference photos

examples of probative evidence

a photo of the lady stealing the neighbors dog

examples of transient evidence

heat/ humidity index, temperature, odor

examples of pattern evidence

imprints, indentations, markings

examples of conditional evidence

light, smoke fire, location, body status

examples of transfer evidence

hairs, fibers

examples of methods of classification

physical - non-physical, real - demonstrative, known - questioned (unknown) , class - individual

identification

the process of determining a substance's physical or chemical identity and using its properties to categorize it as a member group

comparison

process to determining weather two or more objects have a common origin

individual characteristics

properties of evidence that can be linked to a common source with an extremely high degree of certainty

individualization

classify evidence into a group of only one member; its unique

class characteristics

properties of evidence associated only with a group, never one source

class

group of objects that share similar characteristics

What is a transfer

when two things come into contact, material is exchanged

what is Locard's Exchange Principle

exchange of material occurs even of the results are not identifiable or too small to be found

is all evidence transfer evidence

true

unknown

material/sample that is being tested

controls

materials whose source is known; ensures the test is working properly; used for comparison with unknown evidence

positive control

expected to give a positive result when tested

negative control

expected to give a negative result when tested

matrix

substance that surrounds the sample

results

can be positive or negative; when comparing to controls, results can be false

false positive

incorrect positive results; should be negative

when does a false positive occur

when there is no negative control

What is a type one error?

false positive - serious ; can falsely incriminate someone of a crime

false negative

incorrect negative results; should be positive

when does a false negative occur

when there is no positive control

what is a type 2 error

false negative - less serious; falsely exonerate someone from a crime

presumptive test

presume a condition / material to begin testing, can be false and is very sensitive

confirmatory test

confirms a test being done , very reliable