FORENSICS 163: TINY CRITTERS
This essay might be of special interest to writers of detective and mystery novels who would like to enrich their stories by providing their readers with a gift of extra details. It might also be of general interest to many other readers, especially those who are CSI and NCIS fans.
Since scientific terminology often differs in meaning from words of every-day conversations, the patience is requested of readers sufficiently fortunate to have studied basic sciences while a few words to gently fill in gaps are directed at those who have not been so blessed.
In scientific terminology, energy can be defined as an indirectly observed stimulus that manifests itself in many forms. Examples are chemical, elastic, electric, luminous, magnetic, mechanical, nuclear, radiant, sound and thermal energies. Thanks to Albert Einstein, since energy and mass are considered to be equivalent (e=mc^2), we also include mass. Forms of energy can be converted into other forms. A common example is the conversion of energy radiated in the form of electromagnetic radiation in the infrared portion of its spectrum by the Sun into thermal energy that is sensed as warmth on the back of one’s neck during a sunny day. Much like chemical energy released by gasoline while being converted by a process of compression and ignition into mechanical energy in the compression chamber of an automobile engine, radiant energy from the Sun is converted by a process known as photosynthesis into chemical energy that fuels activities of photosynthetic organisms such as plants, algae and a considerable number of species of bacteria.
Included among photosynthetic organisms are diatoms. These are usually single-celled entities whose sizes are expressed in microns (millionths of a meter). Photosynthesis enables diatoms to generate their own food from inorganic substances. There are an estimated 100,000 species of diatoms, and they abound in almost any fresh and marine body of water and even in some simply damp places in the world. They can also be found in air and on skin and clothing. If you have an opportunity to view diatoms through a microscope, take advantage of it. They have porous, outer cell walls (frustules) of nearly pure silica (glass) that bear spikes, spines, pores and other attributes that are even smaller than a micron and that are arranged in intricate and beautiful patterns. If you have no access to a microscope, pictures of diatoms can be easily found on the internet.
In addition to bringing beauty to the microscopic world, diatoms play a fairly important role by using synthesis to create, among other things, oxygen. As most of us know, oxygen is required by all aerobic (oxygen-breathing) life on Earth. Diatoms produce almost one quarter of the oxygen we breath. By virtue of the large number of identifiable, diatom species, they also play a role in forensics.
When a dead person’s body is found in water, among other facts, investigators will want to know where the body entered the water and if the person was alive or dead at the time. A living person, especially if conscious, takes a few minutes to drown. During respiration, water passes through lung membranes into still flowing blood. The blood carries the water into the person’s heart, kidneys, liver, bone marrow, brain, etc. Finding diatoms within these organs indicates that the person was alive when entering the water. The opposite indicates the person was not alive.
A person’s body disposed in a river is often carried downstream by currents. A comparison of diatoms found at locations upstream with those found in water where the body was found and those found within the body can reveal where the person drowned.
An example was a case where a woman’s body was found floating in a river. A postmortem examination indicated that the death was caused by asphyxial results of drowning due to homicide. The location of the drowning became a critical factor in the following investigation. Samples were taken from fluid in the lungs of the body. Water and mud samples were also taken from the body recovery site and from upstream sites along the river. The samples from the site determined to be the entry site were compared with samples taken from a suspect’s training shoe, stocking and T-shirt. There was a match, which, with additional evidence, led to the ultimate conviction of the murder suspect.
What could be more horrific for a mother than having her child drown? Being accused of having drowned the child herself. In another case, the body of a boy was found in an artificial pond. An initial pathology report held the death to be a nonsuspicious, fresh-water drowning. The boy’s mother, however, was suspected of drowning him in a bathtub and then placing his body in the pool. In view of this, the case was reopened. Samples from the pond and from the boy’s lungs were analyzed. They were found to be a match, and the mother was acquitted.
It should be noted that evidence revealed by diatom tests are primarily used in legal proceedings to support other evidence. Additional factors that can be used to support a diatom test when discriminating between water locations include the salinity (saltiness) and pH of water being tested. The symbol “pH” refers to the acidity and alkalinity of a solution. On a scale of 0 to 14, a value of 7 indicates neutrality, less than 7, acidity and more than 7, alkalinity.
Diatoms often colonize, and the succession of their attachments might offer means to determine times of death, which is often a critical factor in an investigation of a death.
Because diatoms preserve well, they provide a record of past environmental conditions.
All attributes of diatoms are not positive. A negative attribute is its tendency to stick to inert surfaces. The worldwide cost of antifouling treatments has been estimated to be some $3 billion.
Since diatoms need sunlight for photosynthesis, they are usually found no deeper than 650 feet in bodies of water. A diatom prevents sinking below that (photic) zone by increasing the volume of a vacuole (chamber) to increase buoyancy.
Deposits of well-preserved diatoms find commercial use in such substances as ceramic, paint, filters, fine abrasives, insulating material, garden pest control and toothpaste.
Our Sun produces almost all the energy driving Earth’s various systems. Solar energy is created by virtue of the gravitational pressure at the Sun’s core forcing hydrogen atoms to fuse and become helium atoms. A statistic illustrating the immensity of this conversion is that 700 million tons of hydrogen is fused into helium every second. This nuclear process maintains the temperature at the Sun’s core at some 27 million degrees Fahrenheit, which causes atoms to discharge photons (basic units of light and other electromagnetic radiation). The photon is absorbed by a nearby atom, which is heated and discharges another photon, which is absorbed by a nearby atom, which heated and so on. A resulting photon reaches the Sun’s surface in about 100,000 years. From there to Earth takes a photon only about eight minutes. Only some 40 percent of the solar energy that reaches our atmosphere make it to the Earth’s surface.