Answer:
Different types of blood spatter patterns are formed based on various factors, including the angle, velocity, and shape of blood droplets, as well as the surface they impact. Here are some common types of blood spatter patterns and how they are formed:
1. Impact spatter: This pattern is formed when a force is applied to a source of blood, such as a punch or a gunshot. The blood is propelled outward in multiple droplets with varying sizes and velocities. These droplets hit a surface and create a random distribution of small stains.
2. Cast-off spatter: This pattern is created when blood is flung off an object that is already stained with blood. For example, if someone wearing a bloodied hand strikes a wall, blood droplets can be projected off the hand and onto the wall, creating a linear or arched pattern.
3. Arterial spurt/gush spatter: This pattern is produced by the pumping action of the heart through a severed artery. The blood squirts out in rhythmic patterns, usually in a linear or projected manner, resembling an arc or a line of relatively large droplets. The spatter can travel an extended distance before gravity takes over.
4. Expirated spatter: This pattern is formed when blood is expelled from the mouth or nose due to forceful expiration, such as from a cough, sneeze, or gunshot wound. The droplets are typically smaller and more dispersed compared to impact spatter, and they may be mixed with saliva or respiratory fluid.
5. Passive drops/drip stains: This pattern is formed when blood drips or falls from a stationary source, usually due to gravity. Drip stains can create circular or elliptical-shaped droplets on surfaces below. The size of the droplets and the height from which they fall can affect the size and shape of the stains.
6. Transfer/contact stains: These patterns occur when a blood-bearing object comes into contact with a surface, leaving behind a recognizable impression or shape. Examples include bloody shoe prints, handprints, or fingerprints.
It is important to note that various factors, such as the surface texture, angle of impact, presence of obstructions, and environmental conditions, can further influence the appearance and interpretation of blood spatter patterns. Bloodstain pattern analysis is a scientific discipline that utilizes the understanding of these patterns to reconstruct crime scenes and aid in investigations.