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

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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

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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

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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?

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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