Plant Clues

by Andrea Campbell

Additional clues about conditions at the crime scene can be found from an examination of living evidence, in this case, plant life. The presence of certain mosses, for example, may indicate a shaded area.

A competent botanist can estimate the age of vegetation found under a body in relation to foliage found in the immediate surrounding area. In one case, a skeleton found in wet Massachusetts ground had become intricately intertwined into a wild network of shrubs, weeds and vines. The evidence was delivered to investigators in two huge blocks of earth! In fact, when the crates arrived, someone said “. . . Along with the bones, they’ve sent us a couple acres of Massachusetts real estate.”

Although examiners like to see the remains—in situ—in the exact same relation it had to the field, this was second best. A careful study of the root system provided them with data on time since death, simply because investigators could determine how many growth seasons had passed.

Also, botanists know that when a root penetrates a bone it keeps growing, and the new developing stems can ultimately break the bone into fragments, imitating other forms of trauma. It would have been impossible to identify the sites of bullet impact on the bones if it had been confused with similar destruction due to later root growth.

Pods, seeds and pollen can also be conclusive evidence. In Arizona a woman’s body was found in the desert under a paloverde tree. Police arrested a suspect who had two paloverde seedpods in the bed of his pickup. Since DNA testing can match parent plants just like DNA on human parents matches their children, the tests proved that the seedpods from the man’s truck matched the tree under which the woman’s body had been found. This living evidence helped to convict the man of murder.

In another case, seeds in a 1960 murder investigation told investigators that the corpse had been moved from the actual murder scene. A cypress tree found in a garden of a particular house also matched seeds and mortar found on the body, pointing police in the right direction. Further evidence built a solid case against a man who was eventually convicted of murder.

Palynology is the study of palynomorphs or pollen. The best thing about pollen besides evidence of the seasons, is that pollen has a predictable production and dispersal rate in specific regions. Consequently when it is found on material at crime scenes, it can lead to a suspect.

Some palynologists believe that O.J. Simpson, a man who was acquitted of killing his wife and an innocent bystander, could have been linked to the case with pollen evidence. If, in fact, Simpson had hidden in the bushes as theorized, his clothing might have picked up pollen spores, placing him at the scene. Pollen evidence found in dirt helped to convict a murderer in Sweden in 1969. In one Austrian case, mud on the killer’s boots linked him to a crime scene, and, once a detective even found pollen in the grease of a killer’s gun and another found pollen in the ink of a document that demonstrated it was a forgery!

Some excerpts from Andrea's book Detective Notebook: Crime Scene Science, for children ages 10 and up.

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Toolmarks and Bombs

by Andrea Campbell

Almost every crime involves a tool. Shovels move dirt when evidence is buried, crowbars are handy for breaking into door frames and safes, screwdrivers sometimes force open windows, pliers help make bombs, and bolt cutters clip through fence. The tools used in executing crimes make scars, scrapes, dents, chips, and grooves, and these marks can be traced back to the source just like striation marks on bullets or the ridges found on fingertips.

Police look for objects bearing toolmarks, photograph them, and, if movable, submit it to the lab. It’s not uncommon for investigators to saw off pieces of door frame, turn in small safes and locked drawers, or bring in bits of metal which may have come from the tip of a knife or the claw-side end of a hammer.

Then when a suspect is identified, they get a search warrant for his home or car and try to match up any found tool with its marks, because every tool is unique. No matter how well a tool is forged and polished, under microscopic scrutiny, one can see minute defects or marks on its strike- or cutting-surface. Plus, slight chips or faults as the result of hard employment are produced each time the tool is used. In Florida, a firearms examiner with the Metro Dade Crime Lab in Miami identified a knife used to make a stab wound. He compared the striations left by the knife blade on bone and cartilage on the victim’s sternum.

To compare toolmarks, the examiner reproduces test marks in a manner similar to “the unknown” crime-scene marks, and then he compares the characteristics of each, looking for a match. In essence then, the marks are duplicated and carefully compared.

Tools can also be a source of trace evidence, carrying on them tiny bits of hair, fiber, paint, and soil. And for its last evidentiary significance, toolmark examiners are qualified to make fracture matches—evidence that puts together a small broken fragment in a match to its whole.

For example, a series of bank robberies on night-deposit boxes was committed using hammers, crowbars, and screwdrivers. The method of removing the boxes was pretty clear, but that was all detectives had and nothing much happened. One night though, an investigator found a tiny piece of broken metal which police held onto as a clue. Later when several suspects were identified, a search warrant was obtained, and police collected broken screwdrivers among the suspects’ tools. The broken metal tip saved from the crime scene earlier, perfectly matched one of the broken screwdrivers found in their possession, and the toolmark evidence was enough to put that gang away.

Explosives, Bombs, and Fire

Evidence collection after a bombing or fire is chaotic, dangerous and difficult. Sometimes K-9 units may be used to sniff out explosives. Certain retrieval robotic units may be employed where the danger of future detonation is possible. Fire evidence is generally collected and put into clean, unused paint cans. Even the most seemingly insignificant fragments may prove helpful. Investigators look for blast-cap fragments, fuses, detonating wire, duct tape, cotton, steel fragments, samples of unexploded materials, and even fertilizer. An important clue to an airplane crash over Locherbie, Scotland, was a small fragment, no bigger than a fingernail, but it was evidence of a detonating device.

Laboratory findings in bombings can include:

• What type of explosive was used, possibly with the aid of a manufacturer's chemical signature, certain inert but identifiable chemicals in various explosives.

• Where the explosion or fire took place.

• Identification of triggering device.

In Utah in 1985, a man killed two people with bombs and a third went off in his own car. After thinking the man might have been a victim, soon the trail of evidence led back to him. A workshop in his house proved to be the location where the bombs were constructed—items were matched to crime scene evidence—and sales people remembered selling him some of the supplies that later became parts for the bombs.

Detailed technical information regarding explosive devices is collected, plugged into the computer, and distributed via national databases. This helps authorities identify serial bombers, the sophistication of the explosive devices being used, and the need for a uniform procedure. The FBI has a Data Bomb Center and the Bureau of Alcohol, Tobacco and Firearms houses an Arson and Explosives National Repository.*

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Life Body Fluid: Serology

by Andrea Campbell

Our bodies have their own little rivers of fluid—namely, blood, saliva, semen, sweat, or fecal matter. Forensic serology is the study of these bodily fluids as related to legal matters. Under the umbrella of this biological body of knowledge, forensic serology scientists detect the presence of blood and study the enzymes and antigens present in red blood cells, or what could commonly be called “blood typing.” You may even know your own blood type whether it is A, B, O or AB in type. (There are also people with Rh-factor blood, another important antigen, and, another story.) Blood from different individuals may differ in the type of antigen on the surface of its red blood cells and the type of antibody in its plasma. Consequently, in a blood transfusion, if the blood groups of the donor and recipient are incompatible, a dangerous reaction occurs involving aggregation or the clumping of red cells of the donor in the recipient’s circulation.

We have about ten pints of blood (or up to six quarts of blood, half plasma and half blood cells) being circulated through our bodies by the circulatory system. The blood is pumped by and through the heart into vessels and veins and transports materials—nutrients such as glucose— and oxygen, to vital organs and tissues for growth and repair. It also carries carbon dioxide and waste products from the tissues for excretion. And hormones are taken to various tissues and organs for chemical signaling, all the while moving digested food from the gut to the liver, and within, too, are immune bodies that are hanging out for the prevention of infection, and which possess clotting factors to help stop bleeding to all parts of the body.

In some crime labs, forensic serologists also take on another hat and become expert in “blood pattern analysis,”—also referred to as blood spatter—which is used to recreate the violent scenarios involved in a crime scene according to the patterns displayed on surfaces around the room.

Crime scene blood is important to real life detectives (and also to mystery writers), because it is often found as the result of homicide, assault and sexual assault. Since blood can be found at different time stages, it can be present as fresh liquid pools, coagulated blood, (meaning the blood has turned to a semi-solid state), dried blood, small drops, or even swiped stains.

When any dark substance is found at the scene it is carefully collected because many things can contaminate blood and it can act as a biohazard to the criminalist collecting it. That is why crime scene technicians will often suit-up wearing latex gloves, surgical masks, eye-coverings and sometimes full coverage gowns. (Yes, the CSI people on TV all have hepatitis according to the way they dress!) And although they might not wear as much PPE (Personal Protection Equipment) as shown in the picture at the right, they will surely wear booties, gloves and maybe even a mask.

The determination of blood is best made by using a preliminary color test and for years, the most commonly used was the benzidine color test. (Benzidine was labeled a carcinogen, so it has generally been discontinued.) The Kastle-Meyer color test was used in its place and basically, the tests are based on the fact that blood hemoglobin possesses peroxidase-like activity. To simplify, these are enzymes that when tested with a reagent will cause the sample to turn a deep pink color. It’s not an absolute however, because potatoes and horseradish will also turn it pink.

Sometimes a powerful light moved across the surface of a crime scene is all that is needed for visual inspection. But if blood is suspected and not readily seen, luminol is sprayed and after about five seconds it will fluoresce in a darkened room. Luminol is prohibitive though, because it will destroy many important blood factors necessary for the forensic characterization of blood.

Microcrystalline tests can be performed on material and there are several tests available but the two most popular are the Takayama and Teichmann tests. These depend on the addition of specific chemicals to the blood so that characteristic crystals with hemoglobin derivatives will be formed. They will also react to other materials that may be present in a bloodstain.

After the blood is in the lab a test is used to find out whether it is human or animal blood. It has to do with a rabbit and chicken egg proteins and it forms a cloudy substance called a precipitin. Another test can be done using a “gel diffusion” test. The sample’s antibodies and antigens will diffuse or move toward one another on an agar gel-coated plate. The extracted bloodstain and the human antiserum are placed in separate holes opposite each other on the gel. This will then be subjected to an electrical field and a specific reaction will be expressed by a line of precipitation formed between the two. The blood is then typed. In 1925, a special percentage of the human population were found to be “secretors,” which means that certain antigens, proteins, antibodies and enzyme traits can be found in other bodily fluids such as saliva, urine, or teardrops.

Today, DNA has replaced the tests for specific enzymes and proteins and while they are more accurate, they are also more expensive, timely, and require an updated crime lab facility. Sometimes it is about expertise, resources, and budget that determines how much bodily fluids are taken into consideration.

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