Forensic Science Section 5
Evidence Assessment
1st step in processing digital evidence The digital evidence should be thoroughly assessed
VSC in obliterated writing requires
2 different inks. One of original writing and the other for the obliteration
BTK abbreviation
Bind, Torture, Kill
Graphology
is not practiced in crime lab
How is Digital Evidence processed?
1. Assessment 2 Acquisition 3. Examination 4. Documenting and Reporting
Directionality
1. Inertia caused by the motion of the droplet forces a wave of blood to form 2. The wave wells up on the opposite point from where the stain struck 3. The stain will point in the direction of the force -If the wave breaks off the parent stain a satellite stain is formed. The satellite stain will point back towards the parent stain
5 key facts about Digital Evidence
1. Many types of crime involve digital evidence 2. Every crime scene is a digital evidence crime scene 3. Digital evidence can be fragile 4. Digital evidence can be easily altered 5. Never assume digital evidence is destroyed
Criminal uses of Digital Evidence
1. Target of a Crime (computer) (stealing credit card information, bank accounts, or birth/death certificates) 2. Computer as instrument of a crime (Stalking (Beyer), Threats, Anonymity) 3. Computers as the Repository of Evidence (Drug, Pornography, Photo ID)
Blood stain documentation
Notes Sketches Photographs
Low velocity
normal gravitational force or an energy of 5ft per second. The size of the spatter is relativity large
What is necessary to determine handwriting?
original document
Is bloodstain evidence reproducible?
reproducible phenomenon -The same physical laws apply to blood as they do for other fluid -*Surface tension, viscosity, gravitational pull and the laws of physic are applied equally* -You don't have to understand the laws that are in effect just recognize the results
A well formed stain is one
that is divided along it's axis the opposite sides are approximately equal
Bloodstain Pattern Analysis
the study of "static" bloodstains.
What is the most critical element in bloodstain analysis?
Target surface. -Smoother the surface the more probable the stain will be usable -Rougher surface will cause the stain to distort -Distorted stains eliminate the ability to decipher anything of value
What does Bloodstain Pattern Analysis bring to the investigation?
the ability to define those events that could or could not have occurred during bloodshed
These bloodstains are normally associated with
the aftermath of a violent event
Types of photographs
-Overall 360 degree shots -Evidence establishing shots; with obvious landmarks -Close ups
When counting cast offs, you need to
Add an additional blow to the number because the first blow is unlikely to have bloodied the objec
Bio-hazards of blood
Aids virus and Hepatitis B
Indented writing detection (simple)
Side lighting
Photocopy Identification
Trash marks
VSC exam of plastic bags
*Dr. Greineder* Called that wife was attacked. Police came, and found a disturbance in soil, found *plastic bag*, and inside was a tool that was used to kill wife. Doctor considered suspect, search warrant of house, found plastic bags that look identical to plastic bag of evidence. *VSC used*, saw that striations were one in the same
Indented writing process (complex)
*E*lectro*s*tatic *D*etection *A*pparatus (ESDA)
How long has blood stain analysis been around?
*Reference exist as far back as 1894 Germany* -1950's, impact angle research began in the U.S. -early 70's, Herbert MacDonnel, brought bloodstain evidence into the forefront -*1983 the International Association of Bloodstain Pattern Analysts was formed *
Forensic Pathology often times answers the question of
*WHAT* of the crime (Bloodstain Pattern Analysis also provides information as to the "WHAT" of the crime)
The majority of forensic disciplines provide information regarding
*WHO* such as DNA, fingerprints, and hair examinations
Close ups
-Macro lens -2 photographs - one with a scale and one without -Use 2 scales for width and length -90 degree photographs
Limitations of bloodstain analyst
-Requires training and experience -Should not be done with limited stains -Only provides parameters -Few true absolutes
Recovering blood evidence
-Use fingerprint method for lifting stains -Dried blood scrapings for serology testing -Cotton swabs to collect wet blood
Impact angle
-When blood strikes a surface a right triangle is created -The triangle exists between the target surface and the line of travel -Using mathematical principles the impact angle can be determined
Aids virus
-Can survive in liquid state for 15 days -Refrigeration or frozen increases survival -Once dried becomes inactive - 1 to 9 ratio of bleach and water mix kills virus in one minute -Wear protective clothing -Use common sense
Video tape
-Different perspective -Enhances relationship of evidence to scene -Can make a quick narration
What information might be discernible to a trained investigator?
-Direction a stain was traveling -Angle of impact -Distance above a target surface the stain originated -Type of force used -Number of blows -Position of suspect or victim during the attack
Uses of bloodstain evidence
-Directionality -Impact angle -Type of force -Number of blows struck
Things to remember about blood analysis
-Do not make an evaluation based on one stain -It is not always possible to obtain all the various types of information -Conclusion must be considered against the relationship of other evidence
Evidence Assessment - Legal Considerations
-Electronic Communications Privacy Act of 1986 (ECPA) -Privacy Protection Act of 1980 (PPA) -USA Patriot Act of 2001
Case Assessment
-Legal Authority -Consult with Case Investigator -Other Forensic Exams
BTK serial killer
Dennis Radar (1974-1991) Wichita, Kansas Communicate with police Computer disc
The exclusion to the high velocity is
Expiratory blood - This blood is less vivid in color due to saliva
High velocity
Force or energy in excess of 100ft per second. -The stains are mist like ranging from 1mm or less in size. *Usually a result of gunshot injuries*
Lindbergh kidnapping (1932)
Found that Richard Hauptmann wrote the ransom note for the Lindbergh's
Does blood travel in a straight line?
NO. Parabola effect
Blood spatter analysis professor
Lt. Craig Gravel
The angle at which blood travels may _______ but it can not ______
increase decrease
Paper Edge Matches
Paper, dollar, stamps
Evidence Assessment evidence considerations/cautions
Prioritize the Evidence Electromagnetic Interference Packaging, transport and storage
String the scene
Process that provides a graphic illustration of where the stains originated
What kind of information do blood spatter analysis provide?
information specific to the events that occurred
What is the shape of blood droplets as it is in flight? Why?
Sphere due to: -Surface tension -Molecular bonding, which causes the liquid to occupy the smallest space possible - sphere -Retains that shape until acted upon by other forces
Velocity refers to the speed of the __________________________ and not the speed of the ___________________
instrument creating the injury blood in flight
Blood does not spontaneously degenerate from low velocity droplets to a fine mist. True or False?
True
Photocopied writing is not suitable for a meaningful handwriting examination. It may not represent an accurate depiction of the original
True
VSC
Video Spectral Comparator Utilizes ALS (alternate light source) to reveal differences in reflective properties of ink and fibers in paper
Plastic bags in VSC look like
barcodes
Skeletonzation
blood begins to dry in 50 seconds. A ring begins to form on the outer edge of the droplet
Using a number of well formed stains you can
establish parameters under which the stain was create
VSC (matche,stamps, dollars)
fibers that connect with match pieces, adhesive in stamps, and fiber in the torn pieces
Medium velocity
force or energy more than 5ft per second and less than 25ft per second. The size of the spatter ranges between 1 - 4mm *Typical of a blunt force trauma*
Using cast off stains it is possible to tell which
hand the assailant held the object
