Blood spatter analysis is vital to forensic science. Also known as blood pattern analysis, It helps investigators piece together the events of a crime from the bloodstain patterns left behind. This technique has played a crucial role in solving numerous cases, and its use can range from determining the victim’s position to identifying the type of force or weapon used. Despite its effectiveness in many cases, blood spatter analysis is still controversial due to its potential for error. So, let’s delve deeper into the science of this fascinating form of forensic science, its uses, its real-world impact, and the challenges it faces.
The Science Behind Blood Spatter Analysis
Types and Patterns of Bloodstains
Blood spatter analysis plays a crucial role in forensic investigations, allowing experts to piece together the events of a crime by examining the bloodstain patterns found at a crime scene. There are generally two categories of bloodstain patterns: passive and spatter.
Passive: these bloodstains result from the force of gravity acting on a blood source, such as blood dripping or pooling on a surface. Examples of passive bloodstains include drops, flows, and pools.
Spatter: Spatter occurs when a force is applied to the source of blood, propelling it in various directions. Depending on the amount of force applied, spatter bloodstains can be further classified into low, medium, and high-velocity impact spatters.
Principles and Methods Used in Analysis
Analyzing bloodstain patterns includes several key elements:
- Directionality: This is all about finding out where the blood came from. By looking at the shape and angle of the blood drips, experts can figure out the direction the blood was moving. For example, blood drops will look more stretched out the faster they were going when they landed.
- Area of convergence: Imagine if you could rewind time and watch the blood drops fly backwards. The area of convergence is the spot on a flat surface where you’d see them come together. This helps to determine where, in relation to this spot, the blood came from.
- Area of origin: This is finding out where the blood started from in a three-dimensional space — similar to the area of convergence, but considers everything in the room, not just a flat surface. To find this, experts use math tricks, special methods, or computer software to consider the paths of many blood droplets.
- Size and spread: The bloodstains’ size and spread can tell investigators much about what caused the injury. Bigger and more irregular bloodstains often mean a forceful hit, while smaller splashes might mean something like a gunshot.
What Bloodstains Can Tell You About a Crime Scene
Blood spatter analysis can yield valuable information during a criminal investigation.
- Understanding the sequence of events that transpired during the crime.
- Determining the position of the victim, assailant, and any objects involved in the incident.
- Identifying the type of force or weapon used, such as a gunshot or blunt force trauma.
- Differentiating between accident, suicide, or homicide scenarios.
- Corroborating or contradicting statements given by witnesses or suspects.
Real-Life Cases Solved through Blood Spatter Analysis
The Murder of Martin Payne (2022)
Martin Payne was murdered on July 8, 2019, a day after James Lee Busch and Zachary Armitage escaped away from William Head Institution in Canada. Busch and Armitage were looking to steal Payne’s banking information inside his home, where the murder took place, leaving a multitude of bloodstains.
Staff Sgt. Trevor Knopp, an RCMP bloodstain pattern and crime scene analyst, played a crucial role in a thorough analysis of the bloodstain patterns at the crime scene. As covered in the Vancouver Island Free Daily, Knopp identified key areas throughout the home, especially near the entrance of the main bedroom and the ensuite bathroom, where the blood spatter patterns suggested Payne was struck. Knopp examined blood transfer stains on a hatchet and a bowie knife from the scene and used the bloodstain patterns to hypothesize a likely sequence of events in the crime.
This detailed blood spatter analysis played a significant role in the trial and conviction of Busch and Armitage. The insights and evidence provided by this analysis painted a clear picture of the crime, helping the jury make a well-informed decision, convicting Busch of first-degree murder. Armitage pled guilty to the same charge during Busch’s trial.
The Conviction of Jeffrey MacDonald
The Jeffrey MacDonald case involved the brutal homicide of MacDonald’s wife and two children at their Fort Bragg home in 1970. MacDonald, a former army doctor, claimed a group of perpetrators under the influence of drugs attacked his family, but investigators were skeptical due to inconsistencies found in the crime scene. This complex case gained national attention and resulted in MacDonald’s conviction in 1979.
Blood spatter analysis played a significant part in revealing the truth behind the events. Army investigators found limited signs of a struggle and blood spatter patterns that implied MacDonald had moved the bodies, contradicting his claims. The blood spatter evidence suggested MacDonald was the likely perpetrator.
The compelling blood spatter analysis helped secure MacDonald’s conviction, and he currently serves his sentence in a federal prison despite still professing his innocence.
The Marissa Devault Case
In 2009, Marissa Devault was convicted of the first-degree murder of her husband, Dale Harrell, in their Phoenix home. The case attracted attention due to salacious details, including a supposed failed attempt to collect life insurance to repay significant loans from Devault’s boyfriend. Devault claimed self-defense, alleging physical and sexual abuse from her husband.
Bloodstain pattern analysis played a significant role in determining the truth of the incident. Initially, Devault alleged that another man residing in their home had attacked Harrell while she was unconscious. However, the analysis demonstrated that Harrell was alone in the bed during the attack. Bloodstains found on Devault’s clothes were consistent with a person swinging an object above their head repetitively, leading investigators to deduce that it was Devault who bludgeoned her husband with a hammer.
Devault’s conflicting accounts, combined with the bloodstain evidence, led to her conviction of first-degree murder. Despite maintaining her stance on self-defense, the jury’s decision was primarily based on the evidence deduced from blood spatter analysis.
Challenges in Blood Pattern Analysis
Blood spatter analysis is not without its controversy, sparked largely by the subjectivity of its application and the potential for error.
A study from the National Institute of Justice reports that bloodstain pattern analysts were incorrect in their conclusions about 11% of the time on average. Even more strikingly, the conclusions of any two analysts contradicted each other at a rate of about 8%. This latter statistic is of particular concern because technical review by a second analyst is a common method intended to prevent errors.
Meanwhile, a report from the National Research Council suggests that the decisions of bloodstain pattern analysts are often more subjective than scientific, leading to potential biases. The report states ‘many bloodstain pattern analysis cases are prosecution or defense-driven, with targeted requests that can lead to context bias.’
Blood Spatter Analysis and the Case of Warren Horinek
In 1996, Warren Horinek called the police to say his wife, Bonnie Horinek, had shot herself. As the investigation unfolded, various authorities did not dispute Warren’s claim about his wife’s suicide and later testified to that in the subsequent murder trial. However, Tom Bevel, a bloodstain pattern analyst hired by the prosecution, provided crucial testimony claiming that Bonnie’s death was not a suicide but a homicide, pointing at Warren Horinek.
Tom Bevel’s analysis was later disputed by other experts, including defense-hired analyst Celestina Rossi, who argued in favor of suicide. However, Warinek currently remains in prison and continues to claim his innocence.
In a piece titled ‘A Bloody Injustice’ in the Texas Observer, author Dave Mann dives deep into the details of this case and explains why many call blood pattern analysis ‘junk science.’
The Future of Bloodstain Pattern Analysis: Technology and Advancements
Forensic investigators are now using digital tools to move beyond the inherent limitations of human analysis.
A recent development instrumental in this shift is the rise of a “3D multi-resolution scanning platform”. This innovative technology allows for a comprehensive and digitized view of a crime scene, provided through different positions. Put simply, investigators can virtually “walk” through the crime scene without disturbing evidence.
Not only does this technique allow for more precise visualization, but it also includes surrounding factors in the crime scene that can aid in piecing together the sequence of the crime. This technology presents exciting new opportunities to identify specific details about the crime, thereby contributing to more accurate analyses.
Blood spatter analysis is a fascinating blend of science and detective work. While the technique presents challenges—like subjective interpretation and potential inaccuracies—they do not eclipse its overall value in forensic investigations. Its capacity to reconstruct the truth from silent, static bloodstains intrigues researchers, investigators, and the public alike.