Science of Solving Murder: Evidence that Leads to the Culprit

Warning: This article will have content that some readers may find unsettling.

Creativity in humans is a powerful force. It can be used to put rovers on Mars or towards committing a heinous act, such as murder. Homicide makes for interesting movies and books (I was obsessed with the Hannibal universe as a kid) and enthralling TV series, especially when George R. R. Martin writes them, because we all love a good mystery and a story brimming with characters that go against acceptable societal standards. Or think about Law & Order or CSI where we see the science and techniques behind crime solving: They are quick, efficient, easy, and in some cases infallible.

However, it used to be much more complicated, even for officials just to track offenders after they committed crimes. A person could simply give any name they wanted upon arrest. So, they had to devise a system that did not rely on names, the most common way at that time was for prisons to track offenders with the Bertillon (Anthropometric) System, which was developed by Alphonse Bertillon. The system relied on extremely detailed photographs and several anthropometric measurements of an individual: body height, outstretched reach of both arms, trunk height, width of head, length of head, length of the right ear, width of the right ear, length of the left foot, length of the left middle finger, length of the left little finger, and length of the left forearm. Each of these measurements were further subdivided into three classes: “small,” “medium”, and “large”. According to the Iowa Department of Public Safety, the choice of using “right” or “left” measurements were completely arbitrary. However, anthropometry is not a very reliable method, as sometimes we can look very similar to someone who is completely unrelated to us.

 Bertillon poster of physical features
Bertillon poster of physical features (NIH)

Take the case of Will West and… Well, William West. Give us a second, we will explain. When Will West was going through the process of being booked into the prison that would be his home for the next few years, the records clerk examining him said something similar to, “What are your previous crimes?” Will West rejected having ever committed a crime before, but the clerk did not believe him and checked the records for his name. The clerk found William West’s file and therefore doubted Will, because he matched the photos contained in William West’s file. It was not until they noticed that William West was already residing in the prison serving a life sentence that they believed him. So, these “brothers” with no relation, with similar Bertillon measurements cast a doubt on the entire Bertillon system of tracking inmates:

Will West and William West
Will West and William West (Iowa Department of Public Safety)

Officials were shocked how similar the two inmates were, including the FBI. This led to adoption of a new identification and tracking system. It had to be more reliable and less complicated than the Bertillon System.

Fingerprints: Non-Unique Unique Identifiers 

In the 1860s, a colonel wanting to deal with pension fraud utilized fingerprints to catch false claims. In the decades that followed, one Argentina mother found her innocence challenged (murdering her two children) when her fingerprints were used to secure her confession and subsequent conviction of murder in 1892.

Fingerprint card, Francisca Rojas, 1892
Fingerprint card, Francisca Rojas, 1892 (NIH)

These successes and others led to the widespread adoption of fingerprinting in prisons, habitual criminals, and even ordinary law-abiding citizens. Which is why you may be fingerprinted in order to work at certain jobs, especially government jobs or to work in school systems, obtain special licenses, volunteer, and when you are suspected of having committed a crime. 

Fingerprint diagram, 1940 Frederick Kuhne, The Finger Print Instructor…Based upon the Sir E. R. Henry System of Classifying and Filing
Fingerprint diagram, 1940 Frederick Kuhne, The Finger Print Instructor…Based upon the Sir E. R. Henry System of Classifying and Filing (New York National Library of Medicine)

Fingerprints…have the unique merit of retaining all their peculiarities unchanged throughout life and afford in consequence an incomparably surer criterion of identity than any other bodily feature.

Francis Galton, English polymath and eugenicist, 1892

Even if Galton, a cousin to Charles Darwin, uttered these words, he was also the one who calculated the probability of two people having the exact same fingerprints. 1 in 64 billion. Considering there have been approximately 107 billion people that have lived on the face of the Earth, it really is an extremely small number, but still a non-zero one. We know that given enough time to trial-and-error, even the smallest possibilities may come true; this is the essence of the infinite monkey theorem.

When Fingerprints Fail

Now, what happens if a murderer uses gloves or cleans up the crime scene so well no fingerprints are found? Or what will we do if the crime is committed in a place where it would be normal to find a suspect’s fingerprints, such as in their own home?

If you follow famous murders, you may be aware of the Jigsaw murders. In 1935, a British doctor became enraged and murdered his wife, Isabella, and her maid Mary who probably saw him commit the murder. Being a skilled medical professional and wanting to hide his murders, he meticulously dismembered their bodies, even taking the time to remove Isabella’s fingerprints, birthmarks, vaccination and surgery scars, several teeth, eyes, ears, and lips to prevent police from identifying them with dental records or composite drawings.

A 1972 FBI composite drawing of D. B. Cooper
A 1972 FBI composite drawing of D. B. Cooper (Wikipedia)

He then scattered their body parts throughout Lancashire, England and police had the monumental task of reassembling two bodies, identifying them, and then collect enough evidence to find their murderer and secure a conviction. Over time, the police recovered the mutilated bodies and had a good idea that they were the missing wife and maid of the doctor. They also interviewed friends that observed suspicious behavior from the doctor the day after the murder and weeks afterwards.

However, it all being circumstantial, they needed more evidence to charge the doctor with the murders. Forensic pathologists John Glaister Jr. and James Brash were tasked with reassembling the bodies and identifying the victims. They were able to superimpose portraits of both victims over an X-ray image of the skulls staged similar to the photograph.

Isabela's face was reconstructed after the Jigsaw Murders.
Isabela’s face was reconstructed after the Jigsaw Murders (NIH)

This was a landmark case in forensic science, with physical characteristics of a skull being used for the first time in a murder case, that not only lead to Dr. Ruxtons being found guilty and sentenced to death via hanging, but also greatly fostering public and professional support for approaching crime through scientific investigation. 

No Body? No Murder?

Finding the body of a victim had always been crucial in convicting a murderer. But in the 1660s, the Campden Wonder case reinforced the widespread idea that a body was needed for a murder conviction that is still commonly believed today.

A man in England disappeared. The police assumed it was a murder and tried to find the murderer or murderers. Eventually, they came to the conclusion that his servant, servant’s brother, and his mother were the culprits of this disappearance. So all three were hanged for his supposed murder. In two years, the man returned. He told the story how he was captured and sold into slavery to the Ottoman Empire. 

I have destroyed her in acid. You will find sludge that remains at Leopold Road. Every trace has gone. How can you prove murder if there is no body?

John George Haigh, murdered Olivia Durand-Deacon, 1849

But things have changed since then. Now, we do not always need the entire body to convict a murderer. Techniques of forensic science have challenged the idea of “no body, no murder” and have made it easier to convict murders when there is no body. Some murderers believing that if they could get rid of the body completely, they would not be charged with murder. So they tried to dissolve bodies in acid – only to have dentists identify dentures or dental records of patients. Or renting woodchippers and a chainsaw to dispose of a body to only have trace amounts of DNA left on the machines. 

Crime Scenes & Bodies

The idea of looking to crime scenes and bodies for evidence really took hold in the forensic world in the late 19th and early 20th century. Frances Glessner Lee, often called the Mother of Forensic Sciences really advocated for this shift and for being more scientific and systematic in criminal investigations. 

New York City crime scene, 1914-1918
New York City crime scene, 1914-1918 (NIH)

In 1946, she began creating 19 elaborate doll houses that recreated real crime scenes to include the most minute of details, that often may go overlooked, especially at the time. She included the angles of bullet holes, blood spatter, arrangement of furniture, and discoloration of bodies. She called them the “Nutshell Studies of Unexplained Death” as she wanted investigators to be trained to determine the cause of death in order to “convict the guilty, clear the innocent, and find the truth in a nutshell.” These doll houses are still in use today. Everything you need to solve a doll house murder is in the diorama, go ahead and give it a try at this link. Lee would advise you to move your eyes in a clockwise spiral. If you can solve it within 90 minutes you are in the big leagues.

Kitchen crime scene, Nutshell Collection, 1940s-1950s
Kitchen crime scene, Nutshell Collection, 1940s-1950s (NIH)

Understanding body decomposition is important in determining the time of death. There are seven research facilities in the world (six in the United States, one in Australia) that help researchers and investigators understand how bodies decompose in the elements (freezing temperatures, being covered by a mattress, tarps, or even wrapped in black or white plastic).

Ariel View of Freeman Ranch
Ariel View of Freeman Ranch (Vox)

The Freeman Ranch associated with Texas State University is the largest body farm in the world, at any given time, roughly 50 donated bodies undergoing different stages of decomposition are scattered throughout the 26 acres.

The Chemistry of Death

Most of us can recognize the smell of death.

This smell is from biochemical changes that happen when a body is going through decomposition stages. During a post-mortem examination a forensic pathologist is trying to determine the cause of death and an understanding the processes of decomposition and death chemistry can lead to understanding the last moments of a person’s life that can ultimately lead to the murderer.

There are many ways to analyze the chemistry of death. For instance, analyzing urine, blood, or the intestines can inform the forensic pathologists of the cause of death. The contents of a stomach and could show the level of digestion of foods they last consumed, giving an approximate time frame for the murder.

Cerebrospinal fluid can also help determine the cause of death. Cerebrospinal fluid is located in your brain and spinal cord can be analyzed for many things. For example, if one had high levels of cortisol (a stress hormone), it could mean a violent death had occurred.

Similarly, investigating the structure of the eye can give a lot of information about death. The vitreous humor is the colorless gel located between the lens and retina that contains many electrolytes.

Vitreous Humor
Vitreous Humor (Wikipedia)

For the analysis of death, the most important chemicals are potassium, chloride, and calcium. When death occurs, the vitreous humor is more resistant to post-mortem changes that occur in the rest of the body and the concentrations of potassium and chloride can be analyzed and inputted into an equation that can help determine the time of death. Generally, as more time passes, potassium concentration will increase as sodium and calcium fall. This is the result of potassium leaking into the blood plasma for equilibrium. The ratio of potassium to sodium decreases linearly with time. While temperature and other factors can influence the levels, age, sex, and cause of death do not have influences.

The Stages of Death

Most of us are probably familiar with the term rigor mortis, the stage of death when the limbs of a body stiffen. But actually, this is considered the third stage of death. Well, it can be the sixth stage, if you consider when cessation of breathing, a heartbeat, and brain activity as “stages of death”. What we mean is this: Death is not an event, it is a process. Therefore, just like there is not a moment when you step into being an adult from your childhood, there is not a moment that you step into death from life. However, scientists name different stages based on arbitrary yet scientific criteria for easier communication. And rigor mortis is only one of them.

Prior to rigor mortis, you have a stage called pallor mortis, where the skin will pale in approximately 15-120 minutes after death. This is followed by the second stage, algor mortis, a reduction of body temperature to the surrounding temperatures. Then comes rigor mortis: the stiffening that sets in as little as four hours after death. Then, the final stage of death, livor mortis. This stage begins 20-30 minutes after death, as gravity starts forcing blood from the upper parts of the body to settle in the lower part of the body and begins to be visible to the human eye as the skin takes on a red-purplish appearance around two hours after death. After 1-2 days the decomposition stages can begin to be in full force, unless hindered.  


Decomposition starts occurring from the moment of death, known as the fresh stage. It is rather mild in physical characteristics, although some blistering of the skin can occur as autolysis begins due to the lungs no longer bringing in oxygen and removing carbon dioxide. This results in the acidification of body tissues and when coupled with other chemical changes, cells begin to lose their cell wall structural integrity that normally keeps enzymes contained. Once these are released, they begin to breakdown other cells and tissues.

As the oxygen levels in the body are depleted the anaerobic organisms in the gut and respiratory tract begin to thrive at greater rates as their aerobic bacteria counterparts die. These organizations start consuming the body’s carbohydrates, lipids, and proteins that eventually lead to clear signs that the body is clearly in stage two, bloat where the level of microbial proliferation produces so much gas and liquids from the digestion processes the body begins to bloat. These gases and liquids will escape through human orifices, such as the mouth, but depending on the level of skin integrity from autolysis and pressure levels of the gas and liquids the body can actually rupture. This smell is often when bodies are reported as being dead. Although, sometimes people can fail to identify the smell and report a body wasting a way in a busy hot city for a week.

Another profession that helps solve murders is a forensic entomologist. Forsenic entomology is the science that investigates the insects that feed on a dead body. For example, if blowflies and flesh flies are able to access a body in the fresh and/or during the bloat stage, their maggots will begin to hatch and feed on the body. These insects coupled with the continued gas production (bacteria) from within the body will degrade the skin further until eventually the skin ruptures thus reintroducing oxygen back to the inside of the corpse and liquids (bacteria digestion and liquefied organs) to the environment. This creates an environment that allows for more areas that insects can lay eggs and more aerobic bacteria digestion.

During this period the corpse will experience a peak of mass loss from the maggot activity and purging of the fluids, this peak is called the active decay stage that typically finishes when the maggots leave the body to pupate before hatching as an adult. The corpse then enters the advanced decay stage as decomposition is severely limited as there is not much remaining of the cadaveric material (the maggots have eaten everything they possibly could and disintegrated into the surrounding environment).

Pig Decomposition Fresh, Bloat, Active Decay, Advanced Decay, Dry Remains
Pig Decomposition Fresh, Bloat, Active Decay, Advanced Decay, Dry Remains (Wikipedia)

At this point in time, the surrounding soil will have high concentrations of carbon, nitrogen and other nutrients, and alterations of pH levels. This will spur increased plant growth around the body and the remaining dried skin, cartilage and bones will become bleached known as the dry remains stage. If all soft tissue is gone from the body, it would be described as being skeletonized.

All of these processes can be influenced by various factors, such as humidity, temperature, insect activities, clothing, rainfall and many more combinations of factors, but typically a body will be in the skeletonization process within 4 weeks. There are exceptions, such as fetuses or newborns that have never digested any foods and therefore will not have microbial flora (bacteria in the gut) that are critical in the decomposition process.

Another exception would be if you are an Ancient Egyptian pharaoh or a communist revolutionary with specialized care your skeletonization process will slow down considerably. Under dry conditions mummies are preserved, even more so in optimal museum conditions. Vladimir Lenin’s body, has had a dedicated team of anatomists, biochemists, and surgeons that have kept his 149-year-old body preserved since his death.

Lenin's preserved body, inside the mausoleum
Lenin’s preserved body, inside the mausoleum (Wikipedia)

In Louisiana, there is a history of burying their dead in vaulted tombs, the most famous being St. Louis Cemetery Number One. This cemetery has approximately 700 tombs, but yet over 100,000 of bodies have been buried in these tombs, that span a square city block. How is this possible?

Vaults in Saint Louis No. 1
Vaults in Saint Louis No. 1 (Wikipedia)

Well, Louisiana is extremely hot and humid most of the year. These tombs act more like ovens that allow new bodies to be buried within the same tomb months (according to a tour guide) or more realistically, 1-2 years after the preceding body.

However, if the body or a mammal is situated in an environment favorable towards preservation, such as extremely cold temperatures, the corpse/carcass can be protected from decomposition. For instance, a 38,000-year-old female mammoth carcass is being displayed in Moscow, Russia, which is considered one of the best preserved specimens of all times.

Yuka the Mammoth
Yuka the Mammoth (RIA Novosti/Vitaliy Ankov)

Professions: How to Solve Crimes

If you enjoy homicides, besides law enforcement you can consider some other alternatives that will have you working like they do in the shows. Forensic anthropologists specialize in recovering, understanding, and identifying human bones. While similar, forensic archaeologists are also trained to study crime scenes and excavation areas, such as recovering cigarette butts and preserving foot prints. Both can assist in investigations that involve war crimes and mass fatalities. The archaeologist can identify soil characteristics and vegetation that form from a mass burial sites during war or genocide an anthropologist can help identify the victims’ sex, age, ancestry and stature even if their flesh and other markers have been destroyed. Forensic anthropologists and archaeologists may work in conjunction with forensic pathologists whose main focus is determining the cause of death by examining a corpse. Forensic entomologists also can aid in determining the stage of decomposition based on insect activity that can tell us about the time of death that can help lead to a murderer.