Criminalistics vs. Criminology
Criminalistics: Scientific examination of physical evidence for legal purposes. AKA Forensic Sciences. Criminology includes psychological angle, looking at motives, traits, behaviors etc.
Basic services in a crime lab
Physical science, biology, fingerprints, firearms, drug chemistry, document examination, photography
Prongs of Daubert
Testability, General acceptance, Peer review, Known or potential error rate, Maintenance of standards and controls
Locard exchange principle
Whenever two objects come into contact with each other, traces of each are exchanged.
Object or material that's relevant in a crime. Can be transient, pattern, conditional, transfer, or associative.
Members of a crime scene team
First police officer on scene, medics(if necessary), investigator(s), medical examiner(if necessary, photographer and/or field evidence technician, lab experts.
What are the duties of the first office on scene?
ADAPT -- Assess the scene, Detain witness, Arrest perpetrator, Protect scene, Take notes
What is the role of a homicide detective?
Document crime scene, interview original patrol officer, examine crime scene with crime scene investigator, pass on necessary info to assisting detectives.
What does a Medicolegal Death Invesitgator do?
Confirm and pronounce death, photograph scene and body, identify deceased if possible, document(sketch) and evaluate body, collect evidence, reconstruct death even, maintain jurisdiction over body, ensure safe conveyance of body, assist family
Frye v. United States (1923)
Scientific evidence is allowed into the courtroom if it was generally accepted in the scientific community
Daubert v. Dow (1993)
- Admissibility is determined by...
-whether the theory/technique can be tested, Whether the rate of error is acceptable(accurate and reliable), Whether the method enjoys widespread acceptance, and Whether opinion is relevant to the issue
Any small pieces of material, man-made or naturally occurring (animal, plant, or mineral) - including hair, fibers, soil, sand, plant material
From hair, you can determine...
Human or animal
Manner in which hair was removed
Hair Cuticle Scales
Differ between species, are named based on appearance.
- Imbricate (HUMAN): flattened
- Coronal: crown shaped
- Spinous: petal like
Air spaces, usually found near the root but may be found throughout the hair shaft
Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair (Humans, generally less than 1/3 // Animals, greater than 1/2)
Human vs. Animal hair
-Human hairs generally more
consistent in color/pigmentation throughout length of shaft, whereas
animal hairs may exhibit radical color changes in a short distance
-Medulla, when present in human hairs, is generally less than 1/3 diameter of hair shaft. Medulla in animal hairs generally occupies an area of greater than 1/2 diameter of hair shaft.
Probative value of soil
- As a result, the statistical probability of a given sample having properties similar to another is very small
- Evidential value of soil is usually excellent
Significance of plant material at scene
1. Plant remains can be found almost everywhere
2. Offers macroscopic and microscopic evidence (pieces of wood, seeds, fruits, leaves, twigs, plant hairs, microscopic pollen, spores, algal cells)
3. Structure allows identification of the plant and allows gathering of other useful info (season, location, where a body could be buried, how long it's been buried, if a suspect was at the scene)
Unit containing a sugar molecule (deoxyribose), a phosphate group and a nitrogen-containing base
4 Bases of DNA
1. Adenine (pairs with Thymine)
2. Cytosine (pairs with Guanine)
3. Guanine (pairs with Cytosine)
4. Thymine (pairs with Adenine)
DNA can be found in...
Can be found in all body cells- blood, semen, saliva, urine, hair, teeth, bone, tissue
Use of DNA Profiling
- To identify potential suspects
- To exonerate individuals
- To identify crime and causality victims
- To establish paternity
- To match organ donors
DNA Typing - Fingerprinting: RFLP
Restriction Fragment Length Polymorphism
Isolation -- separates DNA from cell
Cutting -- using a restriction enzyme to make shorter base strands
Sorting -- by size, using electrophoresis
Analyzing -- the specific alleles for identification
Takes ~10 weeks
DNA Typing - Fingerprinting: PCR
Polymerase Chain Reaction
Technique for making many copies of a defined segment of a DNA molecule.
Denaturation -- separating strands of DNA
Annealing -- Attaching primers
Extension -- Adding the dNTPs and duplicating the DNA
DNA Typing - Fingerprinting: STR
Short Tandem Repeats
Latest DNA Typing method
STRs are locations on chromosome that contain short sequences of 3 to 7 bases that repeat themselves with the DNA molecule.
Higher discrimination than RFLP, less time, smaller sample size, less susceptible to degradation.
Each person has two STR types each gene --one inherited from each parent.
Short Tandem Repeats (STR)
- STR is the latest method of DNA typing.
- STR's are locations (loci) on the chromosome that contain short sequences of 3 to 7 bases that repeat themselves with the DNA molecule.
This method's advantages include a higher discrimination than RFLP, less time, smaller sample size, and less susceptible to degradation.
FBI's CODIS Database
"Combined DNA Information System"
*Requires >4 RFLP markers and or 13 core STR markers
- Found in the nucleus
- Constitutes 23 pair of chromosomes, inherited from both parents
- Each cell contains only 1 nuclei
- Found in mitochondria
- Inherited from the mother
- Each cell consists of thousands of mitochondria
- Can be found in skeletal remains
Blood Droplet Characteristics
- A blood droplet will remain spherical in space until it drops onto a surface
- Once a blood droplet impacts a surface, a bloodstain is formed
- A droplet falling from the same hight, hitting the same surface at the same angle, will produce a stain with the same basic shape
Blood Droplet Volume is directly dependent upon...
the surface or orifice from which it orginates
Shape & Size of Bloodspot depends mostly on...
nature of the target surface:
- texture (rough or smooth)
- porous or non-porous
Blood Stain Transfer
When a bloody object comes into contact with a surface and leaves a patterned blood image on the surface.
Relates to the direction a drop of blood traveled in space from its point of origin
A non-blood bearing object moves through a wet bloodstain, altering the appearance of the original stain
Angle of Impact:
The more acute the angle of impact, the more elongated the stain
90 degree angles are perfectly round with 80 degree angles taking on more of an elliptical shape
At about 30 degrees, the stain will begin to produce a tail
The pointed end of the blood stain FACES the direction the stain is traveling
Point of Origin
Point of Origin - The point of
origin is the spot where the "blow" occurred. It is determined by
drawing a line from the area of intersection straight up to where the
angle of impact would intersect. It may be established at the scene with
use of strings.
- It is the 3 dimensional location from which the blood spatter occurred
Dr. Neal Haskell
Former entomologist. Worked as Forensic Entomology Consultant throughout US. Wrote etymology report attached to autopsy report. Determined coffin flies of back of a car in Anthony case
Gender differences in bones
- The pelvis of the female is wider
- Males have a narrow subpubic angle and a narrow pubic bone body
An experienced Anthropologist can place skulls into what 3 groups?
- Caucasian (European, Middle Eastern, Indian)
- Negroid (African, Aborigine, Melanesian)
- Mongoloid (Asian, Native American, Polynesian)
Teeth are often used for body ID because?
1. Hardest substance in the body
2. Unique to an individual
3. There is usually a good record of our teeth
4. Sometimes pulp remains in tooth - good source of DNA
To prove a poisoning case...
- Prove a crime was committed
- Access to poison
- Access to victim
- Death was caused by poison
- Death was homicidal
Medical Examiner's responsibilities
Identify deceased, establish time and date of death, determine medical cause of death, determine mechanism of death, classify manner of death
Protects Americans against unreasonable searches and seizures. No soldier, Gov agent, or police can search your home without a search warrant.
A constantutional amendment designed to protect the rights of persons accused of crimes, including protection against double jeopardy, self-incrimination, and punishment without due process of law.
Statements that must be made by the police informing a suspect of his or her constitutional rights protected by the Fifth Amendment, including the right to an attorney provided by the court if the suspect cannot afford one.
Chain of custody is maintained by...
-Evidence container must be marked for identification
-Collector's initial should be placed on the seal
-If evidence is turned over to another person, the transfer must be recorded.
Integrated Automated Fingerprint Identification System (FBI's). Police forces can submit samples to be compared to those on this computerized database
Automated Fingerprint Identification System. Computerized fingerprint search systems match prints by comparing the position of which two types of minutia?
Properties of evidence that can be associated only with a group and never with a single source. E.g. Rifling
Marks or features produced by random imperfections or irregularities of tool surfaces. These characteristics can be used to individually associate tool to tool mark. E.g. Manufacture, wear from use, wear from abuse.
Not visible to human eye. Consist of natural secretions of human skin and require treatment to cause them to become visible
-Combined DNA Index System.
-Used for linking crimes and unsolved cases with repeat offenders.
-Requires more than 4 RFLP markers and/or 13 core STR markers.
Provides basic identification of skeletonized or badly decomposed remains.
From a whole bone or part of a bone, the scientist may be able to determine:
Age, sex, race, heigh, previous trauma, body type, possible cause of death.
Human decomposition stages
-Fresh--from moment of death to visible bloating
-Bloated--begin when the abdomen starts to inflate
-Decay--begins when the skins breaks and the gasses escape. Body deflates.
-Post-decayโwhen only 20% or less of the body weight remains
-Skeletal--when only bones and hair remain
How time of death is determined from insect activity?
After death, body attracts insects; time is tracked by metamorphosis/life cycle of bug
Forensic Document Examiner
ACE -- Acronym for Doc. Examiner. Analyzes/compares questioned documents with real ones to verify authenticity
Look at way document is written.
-Language that is used can help to establish the writer's age, gender, ethnicity, level of education, professional training, and ideology.
Ink is analyzed by...
-HPLC--high-performance liquid chromatography