forensic biology jing qiang. content evidence biologic evidence personal identification theory
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Forensic Biology
jing qiang
Content
Evidence Biologic Evidence Personal Identification Theory
What happened ?
Cases: XX year XX in the province, a bombing occurred, several people died and injured.
Scene investigation found that, in the bombing field, there is a point where a bottle of mineral water was found. Except for that, nothing else is informative.
Problems
1 、 The crime scenes were an accident or a manmade one?
2 、 Who did this? 3 、 How to collect evidence associated
with the problem? 4 、 What kinds of evidences are to
collect 5 、 What we are doing ?
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CRIME
+ =
What Happened?
Why Did ItHappened?
Who DidIt?
Crime Scene Evidence Collection Witness, Suspect and Motive Development
Post Scene Evidence Processing Cause, manner, time of death
Investigative Stage Profiling
Means Motive Opportunity
Identificationand Arrest of
Suspect
7
Forensic Pathology
Investigation of sudden unnatural, unexplained or violent deaths
Answer the questions: Who is the victim? What are the injuries, when did they occur, and
how were they produced? 5 manners of death: natural, homicide,
suicide, accident, undetermined
Forensic Biology
Study blood, semen, saliva and other bodily fluids for use in legal cases
Extract DNA from blood for cross reference and case use
Analyze blood stain patterns
Nature of Biologic Evidence
Blood may be encountered as physical evidence in:
Homicides Sexual Assault Vehicular hit-and-run Burglary Other crimes
10
What we are doing Individualization--demonstrating that the sample
is unique, even among members of the same class.
Interpretation--gives meaning to all the information
Reconstruction--reconstructs the case eventsLee, Dr. Henry. Famous Crimes. Southington:Strong Books, 2001
Locating Biological Evidence
Your Eye Touch
Hi-Intensity & Alternate Light SourcesChemical Tests
Enzymatic Tests Immunological Tests
12
Just A Thought
It’s not what you know that hurts you, its what you think you know and it’s not so . . .Mark Twain
How does this apply to forensic science and crime investigations?
13
Evidence Characteristics
Class--common to a group of objects or persons
Individual--can be identified with a particular person or source.
ABO Blood Typing Blood DNA Typing
Preliminary Considerations
Before a crime scene investigator begins documenting and collecting biologic evidence, he/she must recognize the value of biologic evidence and how it fits in the overall events associated with the crime.
Preliminary Considerations
It is essential to document, collect, and preserve biologic evidence.
Improperly collected and preserved biologic evidence can weaken or destroy a potential source of facts in a case.
Preliminary Considerations
Biologic evidence can point the investigator in the right direction for investigative purposes
If the evidence is collected and stored suitably, it can be presented to a judge or jury several years from the time of the criminal act.
Preliminary Considerations
Properly collected and preserved biologic evidence can establish a strong link between an individual and a criminal act.
Biologic evidence or the lack of biologic evidence can bolster or contradict a witness statement or any statements the suspect may have made.
Preliminary Considerations
The most common applications of biologic evidence are:
Finding blood with the victim’s genetic markers (ABO blood type, DNA profile, etc) on the suspect, on something in the suspect’s possession, or something associated with the suspect (such as the suspect’s fingerprints).
Preliminary Considerations
Finding blood with the suspect’s genetic markers on the victim, on something in the victim’s possession, or something associated with the victim.
Nature of Blood Evidence
Bloodstain evidence has two primary categories of examination importance to the crime scene investigator:
A. Bloodstain pattern interpretation
B. Genetic Marker Typing
Preliminary Considerations
Presently, the courts do not recognize biologic evidence as evidence that can be absolutely linked to an individual, such as fingerprints, bite marks, broken fingernails, and handwriting.
If DNA analysis is utilized, then biologic evidence falls into the category of evidence that can be linked to an individual with a very high degree of probability.
Blood Pattern Interpretation
May establish whether or not a crime occurred (murder vs. suicide or accident)
May dispute or corroborate witnesses’ statements.
Can determined from whom the bloodstain pattern emanated. (genetic marker typing)
Biology Unit
Applies the knowledge of biological sciences in order to investigate blood samples, body fluids, hair, and fiber samples
Nature of Blood Evidence
The identity and typing of bloodstains can Assist in establishing elements of the crime Can identify or eliminate a suspect Can be used to corroborate or dispute the
statements of principals when the bloodstains play a part in a reconstruction of the crime.
The proper collection is essential to the quantity and the quality of information from the stains
Disciplines namedForeign 法医血清学 (forensic serology) 法医血型血清学 (forensic blood group
serology)
法 医 血 液 遗 传 学 (forensic hematogenetics)
法医遗传学 (forensic genetics) 法医生物学 (forensic biology)
China The forensic professional directory named Forensic Biology
Section 1 physical evidence and
forensic evidence
Common Examples of Physical Evidence
Blood, Semen, Saliva Hair Samples from body
organs Fingerprints Documents Serial numbers Impressions glass
Soil & minerals Fibers Petroleum residues Paint, plastic & rubber Powder residue Firearms & explosives Wood & vegetative
fragments
EvidenceEvidence The evidence of all the facts that proves The evidence of all the facts that proves the true situation.the true situation.
The Evidence has two fundamental The Evidence has two fundamental characteristics:characteristics:
1. 1. An objective’s existence, An objective’s existence, traces, articles, documents, traces, articles, documents, sound, video, etc.sound, video, etc.
2. 2. The relationship with the facts The relationship with the facts of the case have the facts of the case have the facts objectivelyobjectively
Evidence of the Criminal Procedure Law :
Evidence, documentary evidence
The testimony of witnesses
Statements of victims
The suspect, the confession of the accused and excuse
Expert conclusions
Record of inspection
Audio-visual materials
EVIDENCE
Evidence: Evidence:
Refers to the characteristics Refers to the characteristics of the material themselves of the material themselves has to prove the goods and has to prove the goods and material traces of the real material traces of the real situation of the case. situation of the case.
As an independent form of As an independent form of evidence, physical evidence evidence, physical evidence has different characteristics has different characteristics than other evidence.than other evidence.
Evidence to prove the facts of the case by its material characteristics
Evidence of indirect proof of the facts of the case
For example: a gold shop was stolen and on fire, effective evidence cannot be found due to the fire scene. But the gold shop located at a crossroad, traffic video at that night was available. Investigators brought up the video, a man was seen pushing a bicycle through the crossroads, and tried to pull over to walk by the sideway just before the accident, in the middle of the night. Unfortunately a car just passed by and the light of the car made the look of the man present in the video. According to the analysis of the tape, investigators found out the identity of the man, and cracked down on the theft of the case.
Evidences are less susceptible to subjective factors
Paternity testing, through the analysis of genetic markers, the paternity relationship can be confirmed or excluded.
A4A5 A2A2A1A3 A2A3
A3A3A1A2
Evidence to prove the facts of the case by its material characteristics
External characteristics: shape, color, quantity, weight, and the placing of a location.
Internal characteristics: physical, chemical, biological structure, composition, characteristics, and so on.
Item evidenceItem evidence
Traces of Traces of
evidenceevidence
Instruments and Instruments and
material material
evidenceevidence
Audio and video Audio and video
evidenceevidence
Chemical Chemical
evidenceevidence
Biological Biological
EvidenceEvidence
Classification
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Biological Evidence
Blood Semen Saliva Sweat/Tears Hair Bone
Tissues Urine Feces Animal Material Insects Bacterial/Fungal
Forensically Important Biological Substances
What are the they? Blood Semen Saliva Urine Feces Vomit Fingerprint residue Sloughed off cells
What else? Bacteria Plant material Pollen Viruses
Biological Evidence related with the human Biological Evidence related with the human body is often referred to as forensic body is often referred to as forensic evidence to prove the facts of the case, evidence to prove the facts of the case, its biological composition and its biological composition and properties.properties.
The evidence often require inspection and The evidence often require inspection and identification to find them with the facts identification to find them with the facts of the case.of the case.
Nature of Biologic Evidence
Biologic evidence may be encountered as physical evidence in:
Homicides Sexual Assault Vehicular hit-and-run Burglary Other crimes
Preliminary Considerations
Biologic evidence can point the investigator in the right direction for investigative purposes
If the evidence is collected and stored suitably, it can be presented to a judge or jury several years from the time of the criminal act.
The characteristics of Forensic evidence characteristics of Forensic evidence
11 .. It’s scientific It’s scientific evidenceevidence2. 2. Influenced by environmental factorsInfluenced by environmental factors
3. It’s biological samples 3. It’s biological samples
4. we have to design 4. we have to design reasonable analysis reasonable analysis strategy, select the strategy, select the correct experimental correct experimental methods.methods.
Biologic Evidence
It is essential to document, collect, and preserve biologic evidence.
Improperly collected and preserved biologic evidence can weaken or destroy a potential source of facts in a case.
Biologic Evidence
Biologic evidence can point the investigator in the right direction for investigative purposes
If the evidence is collected and stored suitably, it can be presented to a judge or jury several years from the time of the criminal act.
Biologic Evidence
Properly collected and preserved biologic evidence can establish a strong link between an individual and a criminal act.
Blood evidence or the lack of biologic evidence can bolster or contradict a witness statement or any statements the suspect may have made.
Biologic Evidence
Perhaps the most powerful application of biologic evidence is the ability to absolutely eliminate a person as a potential suspect in a crime.
Forensic evidence discovery, extraction and testing requires the use of science and technology
The evidence The evidence identification and the identification and the facts of the case, facts of the case, whether the relevant whether the relevant information must be information must be between scientific between scientific theory to interprettheory to interpret
SignificanceSignificance
11 .. is a key to solve is a key to solve
criminal casescriminal cases biologic evidence biologic evidence can establish a can establish a strong link between strong link between an individual and a an individual and a criminal act.criminal act.
22 .. is the facts that is the facts that the judgments are the judgments are based onbased on
Forensic evidence to Forensic evidence to help investigators help investigators identify the nature of identify the nature of the case, the incidence the case, the incidence of the time and place, of the time and place, how and why, as well how and why, as well as the people and as the people and objects involved in the objects involved in the casecase..
33 . . is the means is the means to assess other to assess other evidenceevidence
Forensic Forensic evidence the evidence the probative value probative value of a rigorous of a rigorous scientific scientific examination examination confirmed with a confirmed with a high degree of high degree of objectivity and objectivity and reliability, known reliability, known as the "silent as the "silent witness"witness" 。。
The American scholar Herbert McDonnell said: "physical evidence is not afraid of frightening, will not be forgotten, not like witness who may have emotional fluctuation due to the external environment..... In the course of the trial, the defendant would lie, defense lawyers and prosecutors will lie, even though the judge will lie only physical evidence will not lie. "
In judicial practice, the forensic evidence can be used as an effective means of review and identification of the testimony of witnesses and the parties' statements and the support for other evidences.
Section 2 The basic tasks of the biological evidence,
theory and method
BESIC TASKSBESIC TASKS
parentage testingparentage testing Personal identificationPersonal identification
Biologic evidence may be encountered as physical evidence in:
Homicides Sexual Assault Vehicular hit-and-run Burglary Other crimes
Theory and Technology
个人识别的理论个人识别的理论personal identification/individual identificationpersonal identification/individual identification
亲子鉴定的理论亲子鉴定的理论parentage testing/paternity parentage testing/paternity testingtesting
personal identification theory
Analysis of genetic markers of
biological samples collected by the
individual or the crime scene to
determine whether biological samples
were seized is identical, resemble,
similar.
?
Who leave cigarette Who leave cigarette butts??butts??
Cigarette butts are the Cigarette butts are the man left??man left??
"Identical" refers to a person being identical to himself, the "resemble, similar" refers to the two people are the same or in a close relationship.
?
The same identified the judge cases multiple occurrences of Forensic
samples are the same. "Same" refers to a person's own relationship with its own the same"Same", "similarity" refers to two of the same or similar relationship.
Decided by the same method is the method of comparison
Found at the scene or Found at the scene or extract samplesextract samples
Get a sample of the susGet a sample of the suspectpect
"Samples" and "Samples" and "sample" to compare"sample" to compare 。。
Body fluidSuspicious Sperm
Suspects
The blood of the suspect
Genetic markers for individual identification, paternity testing requirements have the following conditions:
Blood typing Enzyme typing DNA Typing
Genetic Marker
1, the specific features of genetic markers
(1) the number of genetic markers (2) the number of individuals who are to
take the number of genetic markers 2, the stability of the genetic markers 3, the reactivity of genetic markers
the specific features of genetic markers
the number of genetic markers
Number of individuals Number of individuals in the populationin the population
The stability of the genetic markers
Nuclear DNA
Mitochondria DNA
3 . The reactivity of genetic markers
Finding blood with the victim’s genetic markers (ABO blood type, DNA profile, etc) on the suspect, on something in the suspect’s possession, or something associated with the suspect (such as the suspect’s fingerprints).
The paternity test theory
Paternity test must detect individual genetic markers to analyze the genetic relationship.
The basic technology
1 、 the chemical method
2 、 Physical method
3 、 computer technology
4 、 morphological methods
5 、 serological methods
6 、 Biochemistry method
7 、 molecular biological methods
8 、 genetics method
Identification of forensic evidence
The examiner should have the following capability
Professionals
1, has the expertise and skills to solve the problems for forensic evidence;
2, has no interest in connection with the case, who could be objective and operate impartial identification;
3, the appraiser must be a natural person, participate the judicial procedure as an individual, the appraiser should be responsible for any expertized conclusion.
conclusion
Scientific Scientific
repeatabilityrepeatability
non-legal judgmentnon-legal judgment
Prospect
In the 1990’s, most crime labs starting relying on DNA analysis to characterize biologic evidence.
A biologic source can now be statistically narrowed down to one person out of several million or even several billion.
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INVESTIGATORS
“The wise forensic investigator will always remember that he must bring all of his life experiences and logic to find the truth. This means common sense, informed intuition, and the courage to see things as they are. Then he must speak honestly about what it adds up to.”
Dr. Henry LeeChief Emeritus for Scientific Services and the former Commissioner of Public Safety for
the state of Connecticut
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