What You Didn’t Know About Blood Spatter Analysis

Whether you’re an up-and-coming forensic analyst or just someone who can’t get enough of CSI, chances are you have heard a thing or two about blood spatter analysis. A crucial component of modern forensic science, blood spatter analysis offers investigators valuable insights into violent crimes. By studying the shape, size, and distribution of blood droplets, experts can reconstruct the sequence of events, identify the type of weapon used, and even determine the position and movement of victims and suspects.

While TV shows like Dexter and CSI have popularized this field, the reality of blood spatter analysis is far more scientific and intricate than portrayed on screen. Although this technique has been used for over a century, it continues to evolve with advancements in technology. Modern tools, such as artificial intelligence and 3D mapping software, now aid analysts in creating more accurate crime scene reconstructions. For instance, a study by the National Institute of Standards and Technology (NIST) demonstrated that incorporating fluid dynamics and statistical models can enhance the precision of determining the area of origin in blood spatter patterns.

Notably, despite its importance, blood spatter analysis is not always foolproof—it has faced criticism for its potential subjectivity and the possibility of human error.

This article will explore fascinating and lesser-known facts about blood spatter analysis, shedding light on its history, scientific principles, and real-world applications. (The original list of seven has been expanded to ten, as of April 2025.)

1. 1. The first modern study of blood stains occurred in 1895.

   Blood spatter analysis, more professionally termed bloodstain pattern analysis (BPA), is not a new technique in the investigation of brutal crimes. In fact, it is thought to have been studied to some degree for centuries. However, the first surviving modern study of BPA occurred in 1895 when Eduard Piotrowski from the University of Krakow published a paper entitled “On the formation, form, direction and spreading of blood stains resulting from blunt trauma at the head”. The rather gruesome study that Piotrowski undertook involved covering one corner of the room with white sheets and studying the blood patterns that appeared as he beat rabbits to death.

2. 2. The Sam Sheppard case, which is thought to have been the inspiration for the television series and subsequent film The Fugitive, was instrumental in expanding the use of blood spatter analysis techniques in the U.S.

   On July 4th, 1954, Marilyn Sheppard, wife of prominent neurosurgeon Dr. Samuel Sheppard, was found bludgeoned to death in the Bay Village, Ohio home that the couple shared. Although Dr. Sheppard claimed to be asleep downstairs when he awoke to his wife’s cries and tried to stop the intruder from killing her, he was convicted of second-degree murder. His conviction was overturned by the U.S. Supreme Court in 1966, and he was granted a new trial, during which he was found not guilty.

   Testimony from the University of California at Berkeley biochemistry professor and forensic science pioneer Dr. Paul Kirk was thought to be integral to the new verdict. The crime scene was extremely bloody and the only blood found on Dr. Sheppard the morning the body was found was on one knee of his pants, which was not at all consistent with the idea that he was the perpetrator. Since that trial, blood spatter analysis has become much more widespread in the criminal court system.

3. 3. There is a difference between blood spatter patterns, blood drip stains, and blood transfer patterns.

   Although they are each a part of the forensic branch of blood spatter pattern analysis, there are distinct differences between blood spatter patterns, blood drip stains, and blood transfer patterns. Blood spatter patterns are what most people generally think of when it comes to blood spatter. These droplets of blood have been acted on by forces other than gravity, either being cast off of a weapon or spraying from a victim onto a surface. 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. It may fall from an open wound on a victim or perpetrator or may drip off of a piece of clothing or a weapon. These types of patterns can help determine in which direction and at what speed the person or object was moving at the time of the blood drip. Finally, blood transfer patterns occur when blood moves between objects by way of a conveyance like a hand, shoe, or piece of fabric. These could be the result of a struggle, or an attempt by a perpetrator to clean up or escape quickly.

4. 4. The surface where the blood lands can have a tremendous impact on the interpretation of the blood spatter.

   Just as the motion of an object or person can determine what a blood spatter pattern looks like, so can the surface onto which the blood spatters. For instance, the same blood spattered on bedsheets, which would absorb blood and therefore distort the patterns, will look much different than the pattern that would exist on a pane of glass, which would cause no distortion, or even a concrete floor, which could lead to ‘satellite’ blood droplets. Blood spatter analysts must take into account the surface as well as the trajectory of the blood in order to determine the facts of the crime scene.

5. 5. BPA is perhaps most often used to confirm or refute the statements of witnesses or suspects present at the commission of a crime.

   While blood spatter analysis can be extremely effective in determining the placement of perpetrators, victims, and weapons during the course of a violent crime, rarely are blood spatter analysts called on to make these assertions on their own. Rather, blood spatter is most often used as a tool to support or refute eyewitness testimony. For instance, a suspect may argue that they acted in self-defense during the commission of a crime, but a prosecutor may be able to call a blood spatter analyst who can offer their expert opinion that the victim was sitting or lying down – hardly on the attack – when the crime was committed, thereby refuting the suspect’s account.

6. 6. A human must lose approximately 40% of his or her total blood volume before he or she is at risk for death from blood loss.

   A typical male has between 5 and 6 liters of blood while a typical female has between 4 and 5 liters. This amount of blood accounts for approximately 8% of a person’s total body weight. When a person loses more than 1 liter of blood, they are likely to become unconscious. But more than 1.5 liters, and death quickly becomes a risk.

7. 7. Blood spatter analysis can be essential in determining the type of weapon used during a crime.

   There are many reasons an investigator may not know what type of weapon was used during a violent crime. Perhaps a murder was committed by a weapon that was hidden or destroyed along with the body. Or perhaps a body is so badly injured that it is impossible to tell how exactly the murder occurred. The different shapes and sizes of blood spatter on the surrounding area can determine the force, weight, and shape of the weapon. For instance, medium-velocity stains are generally caused by a blunt object, a fist, or even a violent spray from a severed artery while high-velocity spatter that creates tiny droplets is more likely to be from a gunshot wound.

8. 8. Advances in Forensic Bloodstain Pattern Analysis

   Recent advancements in computational modeling, machine learning, and digital imaging have significantly improved bloodstain pattern analysis. A recent review by the International Journal of Innovative Research in Technology (IJIRT) synthesizes current research on BPA, highlighting advances in bloodstain classification, pattern interpretation, and reconstruction. Applications in court proceedings and crime scene reconstruction are also discussed. These advancements have increased the accuracy and reliability of BPA, helping investigators to reconstruct crime scenes and inform court proceedings. The review also includes future research directions, including integrating computational modeling and machine learning into BPA software and developing standardized protocols for documentation and digital imaging.

9. 9. A Recent Example of Real-World Applications of Blood Spatter Analysis

   As already mentioned, BPA assists investigators in determining the positions of assailants and victims during a crime, the sequence of events, and the type of weapon used. In a recent case of a Virginia husband who was accused of killing his wife and another man, for instance, bloodstain pattern analysis helped demonstrate that the victim’s bodies had been moved and repositioned after they were fatally wounded, providing critical evidence in the investigation.

10. 10. Challenges and Controversies in Blood Spatter Analysis

    Despite its utility, blood spatter analysis has faced criticism regarding its subjectivity and the potential for human error. The 2009 National Academy of Sciences report highlighted significant concerns about the scientific foundation of several forensic disciplines, including blood spatter analysis, emphasizing the need for more rigorous standardization and research.

    BPA’s shortcomings were clearly on display in the case of David Camm, an Indiana state trooper, who found his wife and two children shot to death in their home in 2000 and was quickly charged with their murders.

    Over the course of three trials, prosecutors presented a succession of bloodstain-pattern analysts who testified that eight specks of blood found on the T-shirt Camm wore on the night of the crime were “high-velocity impact spatter” from the shooting. The defense produced its own bloodstain experts, who argued that the specks in question were actually “transfer stains”—blood that blotted Camm’s T-shirt as he tried to render aid. David Camm was acquitted in 2013 after spending 13 years behind bars. Another man, a burglar with a long rap sheet whose DNA was found at the crime scene, was convicted of the murders and remains in prison.