Bloodstain Pattern Analysis

©2007 Vernon J. Geberth, Practical Homicide Investigation
Reprint: Law and Order, Vol. 55, No. 3, March, 2007
Article Expanded for Research

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Bloodstain pattern analysis can range from the simple to the complex. The trails of blood in a crime scene or castoff blood patterns are reasonably straightforward and understandable. Determining areas of convergence and origin employing string methods or trigonometric methodologies are more complex and call for a trained specialist. The scientific analysis of bloodstain patterns requires extensive training and experience, which goes beyond the normal crime scene process. Furthermore, there are a number of different definitions and opinions by various experts in the field, which tend to confuse the average investigator. Therefore, the author's intention within this article is to illustrate some simple and practical examples of bloodstain pattern recognition and documentation along with photos and description.

The terms used to describe bloodstain patterns, are oftentimes confusing to the average investigator. Such terms as bloodstain spatter or splatter might be used interchangeably. The reference to pattern analysis or pattern interpretation further confuses the issue because the word interpretation connotes subjectivity to the scientific analysis and evaluation of bloodstain pattern evidence. According to the recognized experts in the field the proper term is Bloodstain Pattern Analysis (BPA), which implies a structured approach in evaluating that, which is to be examined. It is one of several specialties in the field of forensic science. The science of bloodstain pattern analysis applies scientific knowledge from other fields to solve practical problems. Bloodstain pattern analysis draws on biology, chemistry, math, and physics among scientific disciplines


Investigators and crime scene technicians need to be cognizant of the potential dangers in handling blood and other biological fluids in the crime scene. The presence of airborne pathogens and other biohazards such as AIDS, hepatitis and hepatitis B, meningitis and even tuberculosis create a potential risk. Investigators should adhere to the following procedures at any crime scene where blood or body fluids are encountered.

The CSI should wear approved disposable gloves while in the crime scene and remain aware that blood and other body fluids may carry diseases. Consider wearing a disposable mask while in crime scenes where airborne communicable diseases such as meningitis or tuberculosis might exist. Wear eye protective and disposable infectious disease gown to protect clothing when exposed to large amounts of blood or other body fluids.

After the investigation is complete, dispose of gloves, masks, and gowns contaminated by blood or body fluids in a biohazard bag and wash hands thoroughly with an antiseptic hand rinse. Before returning to the station, wash hands again with water and a bacterial liquid hand wash, i.e., Bacti-Stat. Restrict the number of investigators on the scene who may come in contact with the scene of the potential infection exposure. Advise any investigators on the scene who may come in contact with the scene of the potential infection exposure.

Decontaminate all equipment used prior to your return to the station. Change clothing contaminated with blood or other body fluids immediately and decontaminate. Dispose of contaminated supplies as recommended in this protocol. Skin provides a very effective barrier for the prevention of infectious diseases. Wash all contact areas as soon as possible after exposure to help prevent contamination. Wounds such as cuts, sores, and breaks in the skin, regardless of the size, provide an entrance for infection into the body and should be properly bandaged. Report all significant exposures to blood or other body fluids within 24 hours of exposure.


Blood is present in most crimes scene involving violence and therefore presents the investigator with additional information to determine the sequence of events, which may have taken place between the victim and the assailant. Bloodstain patterns at the scene or from the clothing of principals in a case can be used to confirm or refute assumptions concerning events and their sequence. In addition, bloodstain patterns can illustrate the position of the victim, such as standing, sitting, or lying. Bloodstain evidence can also show evidence of a struggle.

Furthermore an effective bloodstain pattern analysis can confirm or refute statements made by principals in the case. For example, "Are stain patterns on a suspects clothing consistent with his reported actions? Or, "Are stain patterns on a victim or at a scene consistent with accounts given by witnesses or the suspect"?

Locard's Principle

Locard's Principle that the perpetrator will take away traces of the victim and the scene, the victim will retain traces of the perpetrator and may leave traces of himself on the perpetrator and the perpetrator will leave behind traces of himself at the scene many times is borne out in the evaluation and retrieval of bloodstain pattern evidence.

The prosecution presented an excellent example of Locard's Principle during the O.J. Simpson case. The "Trail of Blood" theory based on the DNA analysis indicated that blood drops at the scene of the double murder of Nicole Brown Simpson and Ron Goldman, as well as blood in O.J. Simpson's Ford Bronco and his residence positively identified O.J. Simpson as the suspect. The DNA analysis of three stains on the console of Simpson's Ford Bronco indicated that droplets were a mixture of blood from Mr. Simpson, the blood of his ex-wife Nicole Brown, and the blood of Mr. Ron Goldman. The famous "bloody gloves" that were presented as evidence provided the crucial linkage. One glove was found at Bundy Drive, the scene of the double homicide. The matching right hand glove was found at O.J. Simpson's estate. DNA testing of the glove found at O.J. Simpson's estate indicated that blood matching Simpson and the two murder victims "linked" him to the murders. DNA testing of the blood on the glove at Bundy Drive matched O.J. Simpson. The socks found in O.J. Simpson's bedroom bore traces of blood from O.J. Simpson and his ex-wife Nicole, who was one of the murder victims.

Crime scene reconstruction and the presence of bloodstains and patterns in the scene are very important considerations in the crime scene search process. The discipline of bloodstain pattern analysis (BPA) considers the location, shape, size, distribution and other physical characteristics of the bloodstains in the scene. Blood flows will always obey gravity. Hence, the presence of blood flow that seemingly does not follow ordinary gravitational pull might indicate movement of the victim or disturbance of the scene by the offender or someone else who arrived in the scene after the event including first responder.

In Practical Homicide Investigation® we encourage first responders and detectives to "Freeze" the scene so that everything is as it was when first discovered in order to assure the recovery of any evidence. Crime scene technicians and/or the ERT's focus on properly documenting the crime scene, through crime scene photographs and crime scene sketches, the recovery and retrieval of crucial evidence and the recognition and classifications of bloodstain evidence to reconstruct events.

He or she is not expected to be able to perform the sophisticated analysis that an expert in bloodstain pattern analysis performs as part of their expertise and training. In some cases the person processing the scene does in fact have the expertise to conduct bloodstain pattern analysis. In either event, the most important concern is the documentation through photographs and diagrams of any bloodstain pattern.


The search of the crime scene is the most important phase of the investigation conducted at the scene. The retrieval of bloodstain pattern evidence begins with the effective search of the scene. Physical evidence refers to any tangible article, small or large, which tends to prove or disprove a point in question. It may be used to reconstruct the crime, identify participants, or confirm or discredit an alibi. Homicide and sexual assault crime scenes usually contain an abundance of physical or trace evidence especially bloodstain pattern evidence. The systematic search, collection, and preservation of physical evidence are the goals of the crime scene search.


Transient Evidence is temporary in nature. It can include odors, temperature, imprints and indentations in soft or changing materials such as butter, wet sand, snow or mud. It also refers to markings such as lividity, or blood spatters on moveable objects. Pattern Evidence is produced by contact. Blood splatter, glass fracture patterns, fire burn patterns, Furniture position patterns, projectile trajectory, tire marks, M.O., clothing or article patterns, and powder residue patterns are considered pattern evidence. Conditional Evidence is caused by an action or event, such as lighting conditions at a crime scene, odor, color, direction of smoke; flame (color, direction, temperature); location of evidence including bloodstain evidence in relation to the body. Transfer Evidence is generally produced by the physical contact of persons, objects, or between persons or objects. It is characterized by the LINKAGE CONCEPT.


There are three basic categories of stain groups based on the concept that the size of the bloodstain compared with the amount of force propelling that bloodstain. These categories refer to the nature of the impact or force causing the stain.

Low-Velocity Impact Blood Spatter (LVIS)
Low-velocity is considered to be a force or energy equivalent to normal gravitational pull up to a force or energy of 5 ft/s (five feet per second). The resulting stain is relatively large, usually 4 mm in diameter or greater.

Medium-Velocity Impact Spatter (MVIS)
Medium-velocity is considered when a source of blood is subjected to a force of from five to twenty-five feet per second. The resulting stains range from 1 to 4 mm in diameter. These type stains are usually associated with beatings or stabbings.

High-Velocity Impact Spatter (HVIS)
High-velocity bloodstains are created when the source of blood is subjected to a force with a velocity greater than 100 ft/s. (100 feet per second). The resulting stain is predominantly less than 1 mm in diameter although smaller and larger stains may be observed. These type stains are usually associated with gunshot injuries.

Multiple spatter pattersn in different forms. There is low-velocity drip, medium velocity drip near toilet bowl, and high velocity on the floor and pooling near the tub.


Practically speaking, the low-medium-high velocity terms can be confusing and have sometimes been used interchangeably. The future of bloodstain pattern analysis will be based on description. Bloodstain pattern analysis (BPA) has established classifications of stains known as taxonomy of stains and the experts in the field have established the classification of bloodstains and patterns based on a taxonomic approach.

A taxonomy is defined as a set of laws or principles for classification. The idea of taxonomy is derived from biology where organisms are classified by shared characteristics of varying degrees that also share a hierarchical relationship. The hierarchical nature of the taxonomy is significant in its application. At the top are broad categories. Moving down the hierarchy, the criteria become more and more refined and thus the conclusion about a classification becomes more distinct.

The bloodstains and patterns are classified based on their physical features of size, shape, location, concentration and distribution. Classification however, is but one step in the overall analysis. Classification sets the stage for the analyst to define more effectively a source event for any given stain.


Gardner and Bevel (In Press and 2004) have grouped bloodstain patterns into two basic categories; Passive stains and Dynamic stains.

Passive Stains
Passive stains result from an action other than a directed force to a blood mass. Examples would the bloodstain found in a crime scene from transfer or loss of blood by the victim. Blood dripping, contact with bloody objects, which can further be categorized as contact patterns, drip patterns, drip trails, blood pools or flows or blood clots.

Dynamic Stains
Dynamic stains are created by forceful events where fluid blood is projected out from a source under some force or compression. Dynamic bloodstain patterns include spatter, castoff patterns, arterial patterns, and splashes. There is an impact mechanism or projection of fluid. Examples of dynamic stains would be Spatter Patterns, Castoff Patterns, Arterial Patterns, Wipe and Splash Patterns, etc.


Spatter Patterns
occur when a blood mass is broken up into droplets. The droplets are projected out from the origin to the surrounding surfaces within the scene. Blood spatter can occur on a variety of surfaces, such as carpet, wood, tile, wallpaper, clothing, etc. The type of surface the blood strikes affects the amount of the resulting spatter, including the size and appearance of the blood drops. Also how the blood was deposited such as dripping blood, spilled blood or blood, which has been projected.

Projected bloodstains are created when an exposed blood source is subjected to an action or force, greater than the force of gravity. The size, shape, and number of resulting stains will depend, primarily, on the amount of force utilized to strike the blood source.

When a droplet of blood strikes a surface perpendicular (90 degrees) the resulting bloodstain will be circular thus the length and width of the stain will be equal. However, when blood strikes a surface at an angle less than 90 degrees the stain will be elongated or have a teardrop shape. It is readily apparent to the trained eye of the homicide detective. For instance the teardrop shaped stains with pointed end always points in the direction of travel.

Directionality of Blood Stains
This graphic illustrates directionality. Passive Blood drop 90 degrees. Dynamic Blood drop with blue arrow indicating direction of travel. Courtesy of Nucleus Medical Art, Inc.

Cast-off Bloodstains
Cast-off bloodstains occur when blood is projected or thrown onto a surface from a bloody object in motion. Examples would be a cast-off from a bloody hammer, baseball bat or other blunt force instrument. Cast-off patterns are usually associated with beating events. Cast-off bloodstains to a certain extent are consistent in size within any given pattern but can vary depending on the size of the weapon, the extent of the bloody injury and the force of the blow.

Cast Off Blood Stains
Cast-off blood stains on the ceiling and ceiling light fixture caused by blunt force instrument.

Arterial Patterns
Arterial patterns result from blood projected into the scene under pressure form the artery or heart. There are distinctive physical characteristic in the arterial patterns, marked with the typical bright red color of oxygenated blood, as well as the spiked appearance of the blood being released under pressure from the breached artery. These patterns are referred to as arterial spurt, spurting or arterial gushing and are used interchangeably.

Pattern Transfer
Pattern transfer occurs when the wet bloody object comes into contact with another surface.

Splash Patterns
Splash patterns occur when a volume of blood is projected into a scene with minimal force characterized by a large central stain exhibiting minimal distortion. There will be very little satellite spatter present. They most often appear as large-volume patterns.

Wipe Patterns
A wipe pattern occurs when an object moves through a preexisting bloodstain. Sometimes the object that wiped through the blood can be identified, for example a broom. In addition the direction can be ascertained.

Saturation Patterns
Saturation patterns occur when blood had been drawn into porous materials such as rugs, cloth, and clothing and usually tend to destroy other blood patterns of interest.

Body Image
Body image patterns occur when the bleeding body has been lying in the blood, which seeps from the wounds. The blood pools form around the outline of the body and as the blood solids separate from the serum the original position of the body is imaged on the surface.


If the crime scene technician is not trained in bloodstain pattern analysis it is imperative that the crime investigators obtain complete documentation of any bloodstains or patterns both with and without rule of measure. Never assume that all the bloodstain patterns belong to the victim. This is particularly true in cases involving multiple stabbings with sharp-edged instruments or weapons. Self-wounding by the offender is a common occurrence. There are some of the classic patterns such as Directionality, Cast-off Bloodstains, Swipe marks, Pattern Transfer, Saturation, Arterial Patterns, Drip Patterns and other examples of bloodstain dynamics, which should noted and documented by the investigator at the scene.

Photographing the Bloodstain Evidence

Recording the bloodstain patterns in the scene is a major facet of the investigation. It is extremely important that this be accomplished before anything is touched or moved at the scene. Photographs should be taken depicting the overall scene followed by medium range and close-up views of the patterns. A scale of measure should be included with the close-up photographs.

Sketches and Diagrams

The crime scene sketch is a simple line drawing that indicates the position of the body in relation to fixed and significant objects in the scene. It supplements both the written reports and the crime scene photographs. Photographs, because of camera perspective and distortion, do not always depict the exact location in which objects are situated or the relation of one object to another. The crime scene sketch is an excellent visual aid, which allows for the removal of unnecessary details and the inclusion of significant material. A sketch f the bloodstain pattern will contain only essential items necessary for the analysis, whereas regular crime scene photographs will be overcrowded with detail.


Bloodstain Pattern Analysis (BPA) is a discipline, which requires formal training coupled with years of practical experience. The discipline of bloodstain pattern analysis considers the location, shape, size, distribution and other physical characteristics of the bloodstains in the scene. The Scientific Working Group on Bloodstain Pattern Analysis entitled (SWGSTAIN) was created in 2002 and has established many of the current protocols.

As the author of Practical Homicide Investigation and Series Editor I encourage investigators to develop an understanding of the applied science of BPA, which can produce strong, solid evidence. I also recommend the following textbooks on BPA. They are Bloodstain Pattern Analysis: With An Introduction to Crime Scene Reconstruction. Second Edition by Tom Bevel and Ross Gardner (In Press 3rd Edition), The Principles of Bloodstain Pattern Analysis: Theory and Practice by Stuart James, Paul Kish and T. Paulette Sutton and Practical Crime Scene Processing and Investigation by Ross Gardner.

Vernon J. Geberth, M.S., M.P.S. author of the textbook, Practical Homicide Investigation: Tactics, Procedures, and Forensic Techniques, FOURTH EDITION, 2006.


Bevel, T and Gardner R., Bloodstain Pattern Analysis with an Introduction to Crime Scene
      Reconstruction, 2nd Ed
, Boca Raton, FL: CRC Press, LLC Inc., 2002
Gardner, Ross M. Practical Crime Scene Processing and Investigation. Boca Raton, Florida:
      CRC Press, LLC Inc., 2004.
James, Stuart et. al. Principles of Bloodstain Pattern Analysis Theory and Practice, Boca Raton,
       FL: Taylor & Francis CRC Press, 2005.

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