The type of injury inflicted and the amount of force used will determine the volume and pattern of bloodstains:
- Sharp force injuries (stabbing) - these injuries are caused by an object with a relatively small surface area, such as an ice pick or a knife. ...
- Blunt force injuries (hitting or beating) - objects inflicting this type of injury are usually larger, such as a bat or hammer. ...
- Gunshot injuries - mist-like spatter caused by bullets entering and exiting the body.
What causes blood spatter patterns in a wound?
Several factors complicate their analysis. For example, during a beating or stabbing, arterial damage can cause the subject to bleed faster or to spurt blood, the latter creating what's known as a projected pattern [source: Dutelle]. In addition to spatters, analysts look for voids, aka blockages.
Why does blood spatter have a different shape?
Blood Spatter. Blood behaves not unlike those spilled water droplets, and the speed at which the droplets travel when they strike a surface, known to analysts as a target, affects their shape. This speed, combined with angle and surface characteristics, also determines how far blood droplets skip or bounce after meeting a barrier.
What does it mean when blood splatter?
Spattered blood is defined as a random distribution of bloodstain that varies in size that may be produced by a variety of mechanisms. Forward Spatter: Spatter projected outward and away from the source, such as an exit wound, is called forward spatter.
What do analysts look for in blood spatter analysis?
In addition to spatters, analysts look for voids, aka blockages. In the case of a high-density spatter, these gaps in the pattern indicate that something in the way, potentially the assailant, caught some of the victim's blowback. Drop size is only one aspect used in analyzing blood spatters.
What does it mean when a spatter is high density?
How does blood behave when it hits a surface?
What causes bullet stains?
Can backspatter cause internal staining?
Can bullets cause back spatters?
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What factors can affect the blood spatter drop?
However, there are a variety of factors that influence the appearance of a blood droplet after it has left the object to which it was previously attached. The surface upon which it lands, the angle and velocity at which it falls, and the volume of the droplet will all influence the spatter appearance.
How do different events affect the pattern of blood spatter?
Interpreting the Patterns When these droplets strike a surface, the shape of the stain changes depending on the angle of impact, velocity, distance travelled and type of surface impacted. Generally, the stain shape will vary from circular to elliptical, with tails or spines extending in the direction of travel.
What properties of blood might affect the spatter patterns it creates?
The texture of the target surface upon which a drop of blood falls affects the size and shape of the bloodstain pattern. Hard, nonporous surfaces will produce circular stain patterns that have smooth edges, but softer, porous surfaces will produce spatter stains that are scalloped or have rough edges.
What are the 3 different types of blood spatter patterns?
Passive Blood Pattern: In the form of flow, pool, saturation, drip/drop, volume. Projected Blood Pattern: Instrumental, expirated, arterial spurt/gush. Impact Blood Pattern: Blood splashes, object splashes, drops, drips, trails, object impacts.
How Does height affect blood splatter?
The height from which the blood falls will affect the size of the stain, with greater heights tending to result in larger bloodstains. Furthermore, the target surface itself will cause an effect, with absorbent surfaces usually producing smaller stains than non-absorbent targets.
What are the 6 patterns of blood spatter?
There are seven bloodstain categories: (1) passive bloodstain; (2) projected bloodstains; (3) impact spatter; (4) cast-off bloodstains; (5) arterial gush or spurt bloodstains; (6) wipe bloodstain patterns; and (7) transfer bloodstains.
What two factors influence the amount of useful information that can be gathered from blood spatter?
The number and location of stains, as well as the volume of blood influence how much useful information can be gathered.
How does the volume of blood affect the spatter pattern?
The volume of the drop of blood also affects the diameter of the bloodstain. As volume increases, so will the diameter of the resulting bloodstain.
How do height and angle affect blood spatter?
The higher the blood drop falls from, the larger the diameter of the blood drop will be on the surface it strikes. 2. What would be the difference between a blood drop that strikes at a steep angle, compared to a relatively flat (lower) angle? The steeper the angle, the longer and thinner the blood drop will be.
How does velocity affect blood spatter?
Increasing velocity of the drop also causes an Increase in the diameter of the spatter in passive drops of blood. Passive drop increases velocity as it falls due to effects of gravity. Velocity increases when drops fall from greater heights, however, patter will not become larger at heights above 7 feet.
What methods are used in a bloodstain pattern analysis?
Six different pattern types, blunt force impact spatter, firearms (back and forward) spatter, cast-off, satellite stains from a drip pattern, transfer and expirated, were used over the two studies.
What does the shape of a spatter stain determine?
The shape and size of these droplets can help to determine the positioning of a victim, the type of weapon used, and the force used in the crime. On the other hand, blood drip stains appear when only gravity works on the blood.
How does the volume of blood affect the spatter pattern?
The volume of the drop of blood also affects the diameter of the bloodstain. As volume increases, so will the diameter of the resulting bloodstain.
What are the different types of transfer bloodstain patterns?
Transfer bloodstains can be further subdivided into: wipes, swipes, smudges and smears.
What can blood spatter tell us about a crime scene?
Information that may be gained with bloodstain pattern analysis include, for example, the position of the individual when the blood was deposited (sitting, standing, etc.), the relative position of individuals at the time of bloodshed, the possible type of weapon used as well as possible mechanisms that could have ...
How does forward spatter compare to impact spatter?
Forward Spatter Pattern - A bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force. Impact Pattern - A bloodstain pattern resulting from an object striking liquid blood.
Bloodstain Pattern Analysis: Forensic Types and Classification
1. Low-Velocity Spatter. These are large separate or compounded drops caused by an impact of fewer than five feet per second; blood cast off from fist, shoe, weapon, dripping, or splashing.
How to measure blood splatters?
1. Drop a drop of blood from a pipette at the same height down to different surfaces (in this experiment is 60 centimetres high from the surface of different materials). 2. Observe the diameter of the blood splatters on different surfaces. 3.
What is blood splatter?
Blood Splatter is one of the forensic evidences. Bloodstains can occur on a variety of surfaces. The type of surface that free falling blood strikes affects the appearance of the resulting splatter. Bloodstains Analysis is the examination of the shapes, locations, and distribution of patterns of bloodstains, in order to provide an interpretation ...
Why does blood not break up?
Blood will not break up unless it is acted upon by force. The force must be great enough to overcome the surface tension of the blood. 2. Blood forms a spherical shape (perfect circular shape) . The spherical shape is caused by the surface tension of the blood. 3.
What causes blood drop to pull itself in both horizontally and vertically?
3. Surface tension causes the blood drop to pull itself in both horizontally and vertically.
What does it mean when a spatter is high density?
In the case of a high-density spatter, these gaps in the pattern indicate that something in the way, potentially the shooter, caught some of the victim's blowback.
How does blood behave when it hits a surface?
Blood behaves not unlike those spilled water droplets, and the speed at which the droplets travel when they strike a surface, known to analysts as a target, affects their shape. This speed, combined with angle and surface characteristics, also determines how far blood droplets skip or bounce after meeting a barrier.
What causes bullet stains?
These are usually caused by gunshot wounds, but they can also result from explosions, power tools or high-speed machinery. These fast-moving drops leave stains measuring less than 0.04 inches (1 millimeter) across. Bullet wounds can produce both back and front spatters.
Can backspatter cause internal staining?
Backspatter can cause external and internal muzzle staining, but in unusual cases the internal stain can also result from the cooling of explosive gases released by the gunshot, which suck the victim's blood into the gun's muzzle [source: Evans ]. 1 2 3 4 …. 5.
Can bullets cause back spatters?
Bullet wounds can produce both back and front spatters. Backspatter, or blowback, refers to blood exiting the entrance wound in the direction opposite the impact [source: Dutelle ]. (Actually, thanks to Newton's Third Law of Motion, backspatter can result from other impacts and traumas as well.) Investigators dealing with such small drops must rule out other sources of blood spray, such as respiration or pinhole arterial pressure [source: Wonder]. Forward spatter, in the direction of the impact, occurs only in the case of an exit wound [source: Dutelle ].
