Reference Citation: Schiro, G. Applications of Forensic Science Analysis to Private Investigation. The LPIA Journal, July 1999.


Applications of Forensic Science Analysis to Private Investigations


George Schiro, MS, F-ABC

E-mail: Gjschiro@cs.com

(337) 322-2724


Everyone who reads a newspaper or watches television is aware of the impact that scientific analysis of physical evidence can have in a criminal case. Fewer people are aware that this type of analysis can also be of great importance in civil cases and other private cases. A crucial piece of evidence in the civil judgment against O.J. Simpson was a set of photographs of him wearing the now infamous “size 12 Bruno Magli shoes” which he denied owning. These photographs established a link between his shoes and the same size and style shoeprints found at the crime scene. This use of physical evidence in private cases seems to be the exception rather than the rule. Because private investigators rely primarily on subject interviews and surveillance, they tend to under utilize or not recognize opportunities to use physical evidence in these types of investigations.

The reasons that investigators do not use physical evidence in private cases vary. Forensic science, with its myriad of disciplines, can be quite complex. The investigator may not understand the nature of the evidence and the type of analysis required. Finances can also be a limiting factor, unless the investigator has a “dream” client. In many cases, the investigator and the client lack the resources to have the evidence scientifically scrutinized. Another problem is the investigator may not know who is qualified to analyze their particular evidence. Not all forensic scientists have the same qualifications and some are more specialized than others. Finally, the investigator may not be able to locate a qualified expert because a field can be extremely specialized. That field may only have one or two people in the country qualified to conduct the examination.

The purpose of this article is to familiarize the investigator with different types of physical evidence, types of private cases where this evidence may be found, and the forensic scientist that would be needed to facilitate and conduct the analysis of that evidence. To find a forensic scientist, the investigator will have to do some research. When one or more potential experts are located, the investigator should ask for references and ask to see a sample of their prior work. The investigator may also contact experts in other forensic science fields to see if they have heard of the expert(s) and if they have an opinion of the expert(s). Once the investigator decides upon a forensic scientist, the investigator can negotiate any fees that may be involved and present the case to the scientist.

As far as evidence goes, everyone is probably most familiar with friction ridge prints, such as fingerprints, palm prints, and bare foot prints. This type of evidence may be found in employee thefts, industrial espionage, or internal security matters within a company. The investigator will need someone who can develop and collect the prints properly. The development may require some specialized chemical treatments, particularly for prints on rough surfaces or prints on paper. For this reason, the investigator needs to work with someone who knows latent print development technology. Usually, people who are crime scene investigators know these development processes. Once the prints have been developed, they need to be compared to the person who is suspected of leaving the prints. This requires a qualified latent print examiner. The comparison may absolutely link that suspect to the item from which the print was recovered.

Another type of evidence that could prove useful in private cases is human or animal bite marks. A dentist that specializes in bite marks is a forensic odontologist. If the bite marks are of suitable quality, the odontologist may be able to positively identify its source. In the private arena, this type of evidence could be found in civil cases involving altercations where one or more of the parties are bitten or in cases of animal attacks. Photography, enhancement, and comparison of the bite marks must be performed by a qualified forensic odontologist.

A firearms and tool mark examiner may be needed if a broken fingernail is encountered in an employee theft or a civil case. Broken fingernails can be compared to the fingernails from a suspect many months or years after the fingernail is found. A firearms and tool mark examiner can compare the stria or lines on the broken fingernail to the stria on the suspect’s nail. The broken fingernail may be positively identified to its source of origin.

Other evidence commonly encountered in private cases is questioned document evidence. This evidence is any type of document that may be suspicious or any type of document that has some other evidentiary value. Questioned document evidence may be associated with will disputes, employee thefts, and internal security matters. A qualified questioned document examiner must analyze these documents. Do not confuse a questioned document examiner with a graphologist or a person who analyzes writing content. Graphologists claim they can make determinations about an individual’s past history and personality based on characteristics found in the person’s handwriting. A questioned document examiner looks for fingerprints, determines the source of handwriting, examines typewritten notes and attempts to match them back to a typewriter, looks for indented writing, analyzes inks, and looks for any document alterations.

In today’s security conscious, high-tech society, still-cameras, videotape, audiotape, and computers are routinely used. Still-cameras, videotape, and audiotape are commonly found in surveillance and security operations. These media can document and provide evidence of almost any conceivable activity. Unfortunately, the images and sounds are not always crystal clear. An imaging specialist or an audio specialist may be able to clean up and enhance the photographs, video signals, or audio signals. This can maximize the value of this evidence.

Computers involved in private cases must be handled very carefully to preserve any evidence contained in the hard drive and random access memory. Computers and disks could be involved in employee thefts, industrial espionage, and internal security matters. If an investigator encounters a computer or related equipment, then he or she should consult a computer scientist for the best way to preserve and decipher any evidence that may be associated with the computer. Make sure that the computer scientist contacted is a true computer scientist who will be able to deliver the information that the investigator requires. Many people these days “dabble” in computers. They may know plenty about one particular system or program, but very rarely will these people know enough to recover all of the information required. Do not use these people when you need to recover information from a computer unless you have established that they are reliable and can handle the job presented to them.

Biological evidence can be very important in adultery cases, paternity cases, civil cases, and insurance cases. Biological evidence can include blood, semen, saliva, other body fluids, hair, and tissue. This type of evidence and its application to a case can vary widely. Semen or a foreign pubic hair found in a pair of underwear or on some bed sheets may confirm an extramarital sexual encounter. DNA analysis on blood samples from a suspected mother, suspected father, and child may prove or disprove a paternity case. Blood or tissue and its location along with blood spatter or transfer patterns could be important in any case involving injury or death. Blood spatter patterns may confirm or conflict with eyewitness statements. Depending on the need, a blood spatter expert, a molecular biologist, a hair examiner, or a forensic serologist (a scientist who studies blood and body fluids) may be needed for these types of analyses. A forensic toxicologist may be required if someone in a case is suspected of being under the influence of a drug, poison, or alcohol. The toxicologist should be able to detect a variety of substances. In these cases, biological material may need to be examined for the presence or absence of the substances. The substance may be one that is passed through the body quickly or it may be one that lasts for many years in the body and still be detectable after a body has been buried for many years.

A firearms and tool mark examiner may be necessary in any civil cases, insurance cases, or employee thefts where a firearm or tool is involved. Functionality of a weapon, identification of a bullet or casing to an individual firearm, or shooting reconstruction based on trajectories, gun powder residue, and casing ejection patterns can be determined in cases of questionable deaths, shooting accidents, and civil actions resulting from firearms use. Tool marks may be present in employee thefts. A firearms and tool mark examiner can determine if a specific tool made a tool mark found on a surface.

Shoeprints and tire tracks may be found associated with employee thefts, civil cases, and trespassing cases. A qualified shoeprint and tire track examiner can positively identify a high quality shoeprint or tire track to a specific shoe or tire. If the track or print is not of high enough quality, the examiner may be able to say the shoe or tire is the same brand, the same size, and has the same pattern as an individual’s tire or shoe. If a set of tire tracks is present, some general information about the vehicle and the tires may be determined based on the distance between parallel tire tracks, the turning radius of the vehicle, tire wear, and the tread pattern of the tire.

Fracture analysis can be one of the most demonstrable forms of evidence analysis. Fractures are randomly formed cracks or breaks found in an object stressed beyond its breaking point. A fracture may cause a single item to break into two or more pieces. One piece may be left behind at the scene of an incident and the other piece may remain in an individual’s possession. Fractures are frequently encountered in vehicular “hit and runs.” A driver strikes someone with a car and a fracture occurs causing a piece of the car to break off and remain at the scene. The driver flees and later the vehicle is recovered. The piece found at the scene can be absolutely matched back to the piece remaining on the vehicle. This places the vehicle at that scene. Fracture evidence may also be found in employee thefts, insurance cases, and civil cases. Anyone who can put together a jigsaw puzzle can perform fracture matches; however, a firearms and tool mark examiner may be needed for subtle fractures.

An arson analyst can be an asset in insurance cases and civil cases involving suspicious fires. The analyst can take debris from the fire scene and analyze it for any flame accelerants, such as gasoline, lighter fluid, kerosene, diesel fuel, etc. Another specialized forensic scientist is a lamp examiner. Lamp examiners are frequently used in automobile accident investigations. By examining the lamp filament, a lamp examiner may be able to determine if headlights were on, if the high beams were on, if the brake lights were on, or if the hazard lights were on at the time of an impact.

A broad category of evidence called trace or transfer trace evidence could be encountered in civil cases, insurance cases, employee thefts, and internal security matters. Examples of trace evidence include fibers, paint, and glass. Trace evidence is any small amount of a substance that may be transferred to another object. For example, if someone breaks through a sheetrock wall and then breaks into a safe by drilling and peeling it, then some of the sheetrock and the safe insulation may get transferred to the perpetrator’s clothing. This trace evidence could be collected from the suspect’s clothing and compared to the sheetrock and safe insulation collected from the scene. The trace analyst uses a wide variety of chemical tests, microscopic examinations, and instrumental analyses to determine if a sample of trace evidence has the same chemical, microscopic, and physical properties as a potential source of the material. Unless the trace evidence has a really unique feature, then the best a trace analyst can say is that both samples have the same chemical and physical properties. Most trace analysts can examine many different substances; however, some trace analysts may specialize in only analyzing glass, paint, etc.

A drug analyst may be required in cases where controlled drugs are involved. These types of cases may include private matters, such as a parent finding an unknown substance hidden in their child’s room, and internal security matters in corporations. The drug analyst can positively identify the substance based on a series of chemical, microscopic, and instrumental tests on the substance.

Civil cases and insurance cases involving structural failure or design flaws may require a forensic engineer to examine the failed product or the structure. By careful examination, the engineer may be able to find the cause of the incident. The engineer may also be able to conduct a different type of fracture analysis. The engineer may be able to tell how much force was needed to fracture a particular item.

Insurance and civil cases involving bones or cremated remains may require the services of a forensic anthropologist. Depending on which bones are present, an anthropologist can determine the sex, race, approximate age, and approximate height of the individual. The anthropologist could also determine if the person had any diseases that affected the bones, if they had any injuries to the bone, and if they had any surgeries conducted on the bone. The anthropologist could also work with a molecular biologist and have DNA analysis conducted on the bone. The bones could also be examined in conjunction with a toxicologist to determine if any persistent poisons, such as heavy metals, are present.

If insects are encountered in a civil case or an insurance case, then a forensic entomologist may be required to determine if insect parts are present, what type of insects are present, or from where they may have originated. Insects may also be associated with decomposing remains. The presence of these insects may allow the entomologist to approximate how long the person was dead. If plant material is present, then a forensic botanist may be helpful. The botanist can identify the plant material based on the vegetation’s physical characteristics or based on its DNA. This could reveal the plant’s point of origin.

A forensic pathologist can be of assistance in wrongful death cases, medical malpractice suits, insurance cases, and civil cases. A qualified pathologist can determine the cause and manner of death. The pathologist can also explain the mechanics behind certain injuries, the effects of disease on the body, and the effects of various treatments on the body. Finally, a forensic psychologist can provide assistance in civil cases and internal security matters. The psychologist can provide psychological evidence that may explain motivations and possible thought processes involved in an incident. The psychologist may also be able to explain why a person reacted in a certain way based upon that person’s prior training.

In private cases, many potential applications of forensic science exist. The investigator must evaluate the case he or she is working and determine if scientific analysis will help the case or clarify any elements of the case. Most forensic scientists will examine the evidence objectively and render an opinion based upon the evidence. The expert’s opinion may support the investigator’s case; however, the investigator should also be prepared to hear that the evidence does not support the investigator’s case. In any case, the scientific analysis of physical evidence can be helpful to the investigator. It may provide him or her with the objective proof needed to support the case or if it disputes the investigator’s case, it might lead the investigator to an alternate solution of the case.