Forensics Expert Explains How to Analyze Bloodstain Patterns | WIRED
TLDRMatthew Steiner, a certified Senior Crime Scene Analyst, educates viewers on the intricate process of bloodstain pattern analysis used by forensic experts. The video demonstrates various bloodstain patterns, such as passive patterns created by gravity or contact, and the impact of different surfaces on the shape of bloodstains. It covers the significance of satellite stains, transfer patterns, and the effects of movement on blood transfer. The demonstration progresses to spatter patterns, which result from an external force applied to an open source of blood, and the calculation of the area of convergence and origin to determine the direction and point of origin of the blood. The video concludes with the interpretation of complex patterns like wipe, swipe, and cast-off patterns, emphasizing the importance of observation and scientific method in forensic analysis. Steiner highlights the complexity and the need for expertise in this field, noting that it requires time, training, and experience.
Takeaways
- 🔍 **Forensic Expertise**: Matthew Steiner, a certified Senior Crime Scene Analyst, explains the intricacies of crime scene forensics and bloodstain pattern analysis.
- 🚨 **Illegal vs. Legal Methods**: The script distinguishes between interesting but illegal methods and the proper techniques used by forensic experts to obtain DNA.
- 🧵 **Safety First**: At a crime scene, safety is paramount to protect investigators from bloodborne pathogens and to prevent contamination of the scene.
- 🧤 **Personal Protective Equipment (PPE)**: Investigators wear multiple layers of gloves, eye protection, and Tyvek suits to prevent the introduction of foreign DNA or fibers.
- 🐏 **Use of Defibrillated Sheep's Blood**: For demonstration purposes, defibrillated sheep's blood is used, which has had the clotting protein fibrin removed.
- 🔍 **Correlation of Patterns to Mechanisms**: Analysts use bloodstain patterns to infer the dynamic forces that created them, providing a window into the events at the crime scene.
- 💧 **Passive vs. Active Patterns**: Bloodstain patterns are categorized as passive (created by gravity/contact) or active (created by external forces), each offering different insights.
- 📏 **Surface Texture Impact**: The texture of the surface where the blood impacts influences the shape of the bloodstain, with smooth surfaces creating even edges and textured surfaces causing scalloping.
- 👣 **Transfer Patterns**: The pattern left when a bloody object comes in contact with a surface can reveal the nature of the object and the direction of movement.
- 🌊 **Flow and Pooling Patterns**: The way blood flows and pools under the influence of gravity can indicate the position of the victim when injured and whether there was movement.
- 🩸 **Spatter Analysis**: The study of spatter patterns, such as impact spatter, can help determine the angle of impact and the origin of the blood source.
- 🔢 **Mathematical Analysis**: Techniques like area of convergence and area of origin calculations are used to determine the location and angle of the blood source.
- 🕵️♂️ **Interpretation of Patterns**: Forensic scientists interpret bloodstain patterns to understand the sequence of events, movement, and interactions at the crime scene.
Q & A
What is the primary concern when entering a crime scene?
-The primary concern when entering a crime scene is safety. This includes protecting oneself from potential bloodborne pathogens and ensuring not to contaminate the crime scene with personal hairs, fibers, or shed DNA.
Why do crime scene investigators wear multiple layers of gloves?
-Crime scene investigators wear multiple layers of gloves when handling evidence to prevent cross-contamination and to protect themselves from potential pathogens.
What is the purpose of using defibrillated sheep's blood in the demonstration?
-Defibrillinated sheep's blood is used because the fibrin, a clotting protein, has been removed, preventing the blood from clotting and ensuring a consistent medium for demonstrating bloodstain patterns.
How does the surface texture affect the appearance of bloodstains?
-Surface texture significantly affects the appearance of bloodstains. Smooth surfaces like plexiglass result in even, round circles, while textured surfaces like tile or rough surfaces like wood create scalloped or spiny edges, respectively.
What are satellite stains and how do they form?
-Satellite stains are smaller stains that originate from a larger, parent stain. They form due to the disruption of the blood drop by the surface it contacts, causing blood to be forced out from the center of the parent stain.
How can blood transfer patterns help in a crime scene investigation?
-Blood transfer patterns, which are passive patterns created when a bloody surface comes in contact with another surface, can reveal the presence of a victim or suspect's impression. This type of evidence can be highly valuable as it often leaves little doubt about the source of the blood.
What is the significance of observing feathering in bloodstains?
-Feathering in bloodstains indicates the effect of movement on blood, showing how the blood was applied and then moved across a surface. This can help investigators interpret movement at a crime scene, such as a hand moving across a surface or a body being dragged.
How do flow patterns reveal information about a victim's injuries?
-Flow patterns, influenced by gravity, can indicate the position of a victim when an injury was sustained. For instance, if a victim had a shoulder injury and was standing, the flow pattern would go straight down their arm. Any deviation could suggest movement or a different position during the injury.
What is the difference between saturation and pooling patterns?
-Saturation patterns occur when blood is absorbed by a surface, like a mattress or bed, while pooling patterns occur on non-porous surfaces where blood accumulates without being absorbed. Pooling can result in slower drying and visible clotting and serum separation over time.
How is the area of convergence used to determine the origin of bloodstains?
-The area of convergence is a method used to determine where blood came from in a crime scene. By drawing lines through the long axis of several elliptical stains, investigators can find a point where these lines intersect, indicating the origin of the blood spatter.
What is the significance of interpreting the relationships between different bloodstain patterns?
-Interpreting the relationships between different bloodstain patterns can help establish the sequence of events at a crime scene. For example, if passive stains are found underneath an object, it suggests the object was placed there after the stains were created.
Outlines
🔎 Crime Scene Investigation: Bloodstain Pattern Analysis
Matthew Steiner, a certified Senior Crime Scene Analyst, introduces the video by discussing the importance of safety and non-contamination at a crime scene. He explains the use of defibrillated sheep's blood, which lacks fibrin to prevent clotting. The video covers three main categories of blood stains: passive patterns created by gravity or contact, transfer patterns resulting from a bloody surface contacting another, and spatter patterns caused by an external force on an open source of blood. Each category is explored with demonstrations, such as dropping blood at 90 degrees to create round patterns, and the effects of different surfaces on the shape of the bloodstains. The concept of area of convergence is introduced as a method to determine the origin of the bloodstains.
🧬 Bloodstain Pattern Analysis Techniques
The video continues with an in-depth look at bloodstain patterns, focusing on how to analyze and interpret them. Techniques such as the use of chemicals like luminol or BlueStar for enhanced visibility, the documentation of transfer patterns in textiles, and the examination of movement effects like feathering are discussed. The impact of gravity on flow patterns and the significance of saturation and pooling patterns in determining the duration and location of bleeding are also covered. The segment concludes with a demonstration of impact spatter using a hammer and blood, highlighting the importance of personal protective equipment and the analysis of spatter patterns to determine the direction and force of an impact.
📏 Measuring and Calculating Bloodstain Patterns
Matthew demonstrates how to calculate the area of convergence and the area of origin using the long axis of elliptical stains to determine the direction of blood origin. He explains the process of measuring the length and width of stains to find the angle of impact using the arc sin function. The video emphasizes the importance of precise measurements, suggesting the use of millimeters and digital calipers. It also touches on the three-dimensional aspect of bloodstain analysis, considering the height from which the blood may have originated. The paragraph concludes with a discussion on the importance of using multiple methods for analysis to ensure accuracy and account for potential errors.
🕵️♂️ Interpreting Bloodstain Relationships and Patterns
The final paragraph delves into the interpretation of bloodstain relationships and patterns to understand the sequence of events at a crime scene. It discusses the significance of observing passive stains under objects, which suggests the timing of their placement. The video describes various patterns such as passive drip patterns, wipe patterns, swipe patterns, cast off patterns, and voids in spatter patterns. Each pattern type is associated with specific scenarios that might occur at a crime scene. The importance of careful observation and the combination of art and science in forensic analysis is highlighted, emphasizing that the process is complex and requires time, training, and experience. The video ends with an encouragement note for the viewers to have learned a lot from the presentation.
Mindmap
Keywords
💡Crime Scene Analysis
💡Bloodstain Pattern
💡Passive Patterns
💡Surface Texture
💡Satellite Stains
💡Contact Transfer Stains
💡Feathering Effect
💡Flow Patterns
💡Saturation and Pooling
💡Impact Spatter
💡Area of Convergence
Highlights
Matthew Steiner, a certified Senior Crime Scene Analyst, explains crime scene forensics and technique critique.
The presentation covers how to analyze various bloodstain patterns ranging from easy to difficult.
Safety is emphasized as the primary concern at crime scenes to protect investigators and prevent contamination.
Different protective gear such as gloves, eye protection, and Tyvek suits are used to prevent contamination of evidence.
Three main categories of blood stains at crime scenes are discussed: passive patterns, transfer patterns, and spatter patterns.
Defibrillated sheep's blood is used for demonstration, which has had the clotting protein fibrin removed.
Bloodstain pattern analysis correlates the appearance of bloodstains with the mechanism of their creation.
Passive patterns like blood drops at 90 degrees on different surfaces reveal the impact of surface texture on bloodstain shape.
Satellite stains, caused by blood being forced out from a parent stain, can indicate the nature of a disruption.
Contact transfer stains can provide evidence linking a suspect to a crime scene through their unique impression.
Feathering effect in bloodstains can help interpret movement at a crime scene, such as drag marks from a moving victim.
Flow patterns and pooling can indicate the position of a victim and the duration of bleeding at a crime scene.
Spatter patterns result from an external force applied to an open source of blood, such as from a blunt force trauma or a gunshot.
Area of convergence is calculated by drawing lines through the long axis of several stains to determine the origin of the blood source.
The angle of impact on bloodstains can be determined by measuring the length and width of the stain and applying the arc sine function.
Area of origin is calculated using trigonometric functions to determine the spatial location of where the blood source was.
Interpreting relationships between different bloodstain patterns can reveal the sequence of events at a crime scene.
Void patterns in spatter can indicate the presence of an object that has since been removed from the crime scene.
The process of bloodstain pattern analysis is complex, requiring time, training, and experience for accurate interpretation.
Transcripts
Browse More Related Video
Forensics Expert Examines 20 Crime Scene Investigations from Film & TV | Technique Critique | WIRED
Chemical Method for detection of spot in paper chromatography || paper Chromatography
Art inspired by mathematics | Michael Naylor | TEDxTrondheim
Mathematics is the sense you never knew you had | Eddie Woo | TEDxSydney
IR Spectroscopy and Mass Spectrometry: Crash Course Organic Chemistry #5
Chaos Game - Numberphile
5.0 / 5 (0 votes)
Thanks for rating: