1. Stain Patterns of Blood
The location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding.
Surface texture and the stain’s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain.

2. Bloodstain Pattern Analysis Terms
Spatter – Bloodstains created from the application of force to the area where the blood originated.
Origin/Source – The place from where the blood spatter came from.
Angle of Impact – The angle at which a blood droplet strikes a surface.
Parent Drop – The droplet from which a satellite spatter originates.
Satellite Spatters – Small drops of blood that break of from the parent spatter when the blood droplet hits a surface.
Spines – The pointed edges of a stain that radiate out form the spatter; can help determine the direction from which the blood traveled.

3. Bloodstain Pattern Analysis
How can an investigator use bloodstain patterns to analyze a crime scene?
Location & description of individual stains & patterns
Direction a blood droplet was traveling by calculation angles of impact
Area of origin of blood source(s)
Type of object used in attack (edged, blunt, firearm, etc.)
Minimum number of blows
Positions of the victim, suspect, and objects during events
Sequence of events

4. Stain Patterns of Blood
Surface texture is of paramount importance.
The harder and less porous the surface, the less spatter results.
Direction of travel of blood striking an object may be discerned
The pointed end of a bloodstain always faces its direction of travel.

5. Stain Patterns of Blood
Impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion.
At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated.
Origin of a blood spatter in a two-dimensional configuration can be established
By drawing straight lines through the long axis of several individual bloodstains.
The intersection or point of convergence of the lines represents the origin point.

6. Bloodstain Pattern Analysis
Evidence from bloodstain pattern analysis is not usually powerful enough on its own to convict someone of a crime.
It can be useful in supporting other types of evidence found at a scene.

7. Bloodstains Passive, Projected, Transfer
Passive Bloodstains
Patterns created from the force of gravity
Drop, series of drops, flow patterns, blood pools, etc.
Projected Bloodstains
Patterns that occur when a force is applied to the source of the blood
Low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains
The pattern created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.
Wipe pattern from an object moving through a bloodstain or swipe pattern from an object leaving a bloodstain

8. Testing for Seminal Stains
Many of the cases sent to a forensic laboratory involve sexual offenses, making it necessary to examine exhibits for the presence of seminal stains.
The best way to locate and at the same time characterize a seminal stain is to perform a color test for the enzyme secreted into seminal fluid.
A purple color indicates the enzyme is present.
Semen can be unequivocally identified by either the presence of spermatozoa, or of p30, a protein unique to seminal plasma.
Can successfully link seminal material to an individual by DNA typing.

9. Rape Evidence
A rape victim must undergo a medical examination as soon as possible after the assault.
Appropriate items of physical evidence including clothing, hairs, and vaginal and rectal swabs can be collected for subsequent laboratory examination.
All outer and undergarments should be carefully removed and packaged separately in paper (not plastic) bags.
Bedding, or the object upon which the assault took place, may also be carefully collected.

10. Rape Evidence
If a suspect is apprehended within 24 hours of the assault, it may be possible to detect the victim’s DNA on the male’s underwear or on a penile swab of the suspect.
Items routinely collected from the suspect include all clothing, pubic hair, head hair, penile swab, and a blood sample or buccal swab for DNA typing.
The forceful physical contact between victim and assailant may result in a transfer of such physical evidence of blood, semen, saliva, hairs, and fibers.