A Foreword regarding Fire Investigation: Some Fire investigation experts argue that fire investigation is as much an art as it is a science. The engineers argue that it is a science and there is no art. There is a good argument that there is a sound scientific basis for how fire acts but the interpretation of this activity can be extremely subjective. As a result many experts disagree. They disagree on findings, they disagree on conclusions, they disagree on methodology, they disagree on texts and manuals and most of all they disagree with each other. What they shouldn't disagree with is the concept that improved education will improve the fire science profession. In order to investigate and testify about fires an investigator must be familiar with and use NFPA's 921, "Guide for Fire and Explosion Investigations." This manual has been the subject of controversy within the fire community but is recognized as the only peer reviewed scientific method of fire investigation. Kirk's Fire Investigation is probably the least controversial text in the fire science area. J.D. DeHaan, the author of Kirk's has been involved with NFPA since 1990 and has written Kirk's to coincide with the subject matter in NFPA 921. This enhances the experience for the student and increases the integration of both resources into a comprehensive overview of fire and arson investigation.
Most arson fires do not involve elaborate triggering
mechanisms, days or months of planning, or even skilled perpetrators. The crime of arson is “At common law, the
malicious burning of the house or outhouse of another.” In several states, this crime is divided into arson in the first,
second, and third degrees, the first degree including the burning of an
inhabited dwelling-house in the nighttime: the second degree, the burning (at
night) of a building other than a dwelling –house, but so situated with
reference to a dwelling-house as to endanger it; the third degree, the burning
of any building or structure not the subject of arson in the first or second degree,
or the burning of property, his own or another’s with intent to defraud or
prejudice an insurer thereof. State v. Jessup, 42
Most cases of arson involve revenge, vandalism, concealment of another crime, excitement and last, but probably most common, profit. Because the reasons for arson are so varied, the fire investigator must have a special set of skills. In good times suspicious fires are less frequent, in hard economic times they are much more prelevant. The key to a suspicious fire is more often in the financial condition of a suspect or business than in the fire remains. Proving the crime of arson in court depends on adequate proof in both areas, origin and cause and evidence of motive and opportunity to committed the crime.
Origin and cause is a term that the investigator will become very familiar with. A Fire investigation determines the origin, where the fire started, and the cause of the fire. If it is determined that a fire was caused by being deliberately set, an arson investigation starts. The arson investigation determines who deliberately set the fire and utilizes evidence collected by the fire investigation and the evidence specific to the arson investigation to indict, arrest and prosecute the individual responsible.
In the easiest arson cases, someone will run right up to the policeman or fireman on the scene and tell them that “Johnny did it”, he was mad at his brother and set his house on fire, he didn’t mean for it to go this far.” In other cases it may take a few more days of questioning the family members or owners of the business that burned to determine who caused the fire. Just because the solution is easy doesn’t mean that the whole investigation process does not have to be completed. Arson is a felony. Whether the family wants to prosecute or not is irrelevant. The prosecutor in most jurisdictions has the right to prosecute even if the victim does not want to press charges. The insurance company must also be considered. If the company has paid then there will be a prosecution. The insurance company has implicit property rights by means of a signed insurance agreement with the owner of the property. In these cases you still have to identify the source of the fire; what was used to start it, and take evidence samples for lab analysis. Don’t fail to follow procedures just because the arsonist was easy to identify. The court may later exclude his statement or the witness may leave town or die before the trial.
In a well-planned arson, almost anything can happen. The structure could completely disappear or there could be enough of the structure remaining to identify burn patterns, fix the origin of the fire, and determine what, if any, accelerants were used. Often, what evidence doesn’t burn is obliterated by firefighters, whose mission, after all, is to put out the fire as quickly as possible. If you are a fireman assigned the responsibilities of arson investigation for your department, brief your fireman on what to look for at the scene of a fire; have them also try to keep the scene as much in tact as possible. One side comment--all firemen should be on the lookout for the odor of gasoline or turpentine or other accelerants when they initially arrive at the scene.
In most other investigations, the investigator or engineer has an intact scene that he/she can work with. A fire investigation starts with devastation. In order to successfully investigate fires the investigator must know the science of fires, how they start, how they progress and what indicators are left to help reconstruct what occurred. A fire investigator without a good grounding in fire science is at an extreme disadvantage which can ultimately lead to perpetuators going free or innocent people being charged or falsely accused.
In defining our terms the first two are “fire investigation” and “arson investigation”. One is not necessarily the same as the other. Fire investigations are started in nearly every fire to determine the origin and cause of the fire. Usually the cause is accidental, a pot of grease on a stove, an electrical malfunction, a burning cigarette. Some times it is on purpose. When there is evidence that could lead to a conclusion that the fire was purposely set, then an arson investigation ensues. The fire investigation must be handled very carefully, following all the rules of court admissibility even if most of the time it is accidental. If the fire is suspicious then the evidence must be collected properly and the second phase of the investigation must be commenced. The arson investigation centers around how was it done, who had the motive, and is the evidence necessary to arrest and prosecute the perpetrator available. Most arson cases are circumstantial. Blacks law dictionary defines circumstantial as “Evidence of facts or circumstances from which the existence or non-existence of fact in issue may be inferred.” So circumstantial evidence is not hard, physical evidence, but rather circumstances from which fact can be inferred. The facts used to prove motive are derived from financial records, statements of neighbors, credit reports, past history and many more. More on the investigation in Unit 8.
Many firemen and policemen have heard the following myths of arson investigation: (a) the fire destroys all the evidence so there is no evidence to prosecute (b) the firemen believe arson is a crime so the police department should investigate it (c) the police believe the arson is a fire so it should be the fire department’s responsibility. These myths cause confusion and problems in the proper investigation of fires. Fire and Police departments within the same jurisdiction should have a good understanding and work relationship as far as who is responsible for what. This working relationship is the only way to effectively investigate and prosecute in arson cases. Some jurisdictions give the sole responsibility of suspicious fires to the State Fire Marshal’s office. Even if this is the case in your jurisdiction there should still be a hammered out agreement between all of the concern agencies as to how fires should be handled.
Even with a good working relationship between the fire, police and State Fire Marshall, there are still others that have a responsibility for fire investigations. When put together, the parties frequently get in each other’s way and can cause difficulties in working together. Cooperation should be the key to fire investigation. Someone has to be in charge of the scene and regulate who goes in and when they go in. The fire department should be trained to do only as much damage as is necessary to put the fire out and then secure the scene for their investigator, the fire marshal or the police, whichever agency has primary responsibility for investigation.
Once the official investigation is completed at the scene, properly documented, and the evidence collected and preserved, the scene can be turned over to insurance company investigators, engineers and private investigators who have a need and the legal right to examine the scene for their insured(s) or clients. A properly examined and documented scene by public officials, in most jurisdictions, is available to private parties, unless criminal charges are pending. The reason why it is not a big issue is that usually the private parties are the owner’s insurance company, which should have a cooperation clause in the insurance contract, and the owner himself. The owner would need his own investigators if the insurance company denies coverage or the claim or if there is criminal charges pending against him. It is difficult to deny the owner access to his own property after the initial official investigation is complete. If charges are filed, once the case is disposed of, the photographs, reports and documentation collected by the governmental investigators (fire, police, and fire marshal) should be available. If the investigator works in a state where this is information is not accessible then he must respond quickly and talk in detail with the first people at the scene.
Cooperation between all of these parties is a must. All are entitled to information about the fire and all have the same goal, to determine the origin and cause, document the loss and determine if the fire is of a suspicious nature. Public officials should cooperate and accompany privately hired engineers and fire investigators to the scene. A lot can be learned from these individuals. It also helps the engineers and fire investigators to share information with investigators who were on the initial fire scene and know what has been disturbed, what samples were taken and from where.
As a preface to the discussion of the collection and preservation of evidence, it should be noted that the officer processing the scene has to have a legal right to be on the scene. This is governed by case law. Case law is the history of court cases that have decided certain issues in the past. As an example, the issue of an individual’s rights was decided in the “Miranda” case. There is Court made law pertaining to fire investigations as well. It is most important that the investigator know what his rights are to enter a fire scene and how to comply with the rules set down by the courts. An Investigators case will be lost if he/she does not following the proper procedures.
The case law (Kirks p424-29) gives the investigator a specific time frame to accomplish his investigation. Fewer than two percent of suspicious fires result in prosecutions. The officers who take these cases to trial are the experts in what the courts will accept and reject as proper permission to be on the scene. Cases indicate that a fire department has a right to determine the origin and cause of a fire they have responded to. If this is done immediately after the fire (even with police present), evidence collected at that time is admissible. It has even been ruled admissible for the fire department to return to the scene if the debris is still to hot to process, but it has to be a reasonable time, maybe four hours later or so. If the investigator returns later that day, the next day, or stops in periodically over the next week or two, the evidence is most likely inadmissible. Once the fire department leaves, any re-entry to the scene should be accomplished legally with a signed consent by the owner, an administrative warrant, or a criminal search warrant. (Kirk’s p425, consent form). The use of an administrative warrant should cease as soon as there is probable cause to believe that a crime has occurred. At that time the scene should be secured and a criminal search warrant should be prepared.
For many fire and policemen, this may seem like a hassle. It is much easier to march on the scene and do your thing. If you want to successfully prosecute a case of arson you must pay rigid attention to the rules—even if arson is not an initial factor. Consult with your local prosecutor and work out a checklist to be legally on the scene.
An arson investigator can separate evidence collected at a fire site into three categories:
1. Trace and physical evidence regularly associated with crime scenes.
2. Evidence used to identify accelerants or contributing hydrocarbon based fuels.
3. Documentation of evidence used to determine the origin and cause of the fire.
Trace and physical evidence. These terms are redundant, but are used separately because they infer different types of evidence. Trace evidence can be traces of any number of substances collected at a crime scene that can be indicators of who committed the crime. Trace evidence is hair, fiber, blood, semen, dirt, dust, shavings or traces from clothing, etc. These traces can point back to or connect the alleged perpetrator with the crime scene.
For instance, traces of gasoline on the clothes that the suspect was wearing. Traces of black powder in a case involving a bomb. Traces of metal shavings on the suspect’s clothes that were found at the scene and at the home or shop of the accused linking the suspect to both areas. Gunshot residue on a suspects hands right after a shooting. These are examples of the use of trace evidence. Physical evidence is evidence of the crime such as tools, tool marks, gas cans, wicks, rags, molitov cocktail remnants, guns, bullets, knives, etc. Remember fingerprints. Fingerprints on gas containers are a great way to link a suspect to a fire.
In the late sixties and early seventies, as a result
of race conflicts and the Vietnam War, there were riots in several major
cities. These riots involved arson,
vandalism and theft. In 1970 in
While waiting for the fire department two elderly gentlemen drove up and asked me to get in the car with them and ride around the block. They told me that outside agitators were to blame for the problems and that they knew who was responsible for all of the fire bombings. McKenzie Red was his nickname, but they gave me a full description of him as being a red haired African American and that he was across the street from the fire watching what was happening. As we rounded the corner back to the scene McKenzie was not there.
At each of the fire scenes I had carefully preserved each of the bottles and cloth wicks. In writing my report I indicated to the detectives what I had learned about the suspect and what I felt the evidence might show. In conclusion, the suspect’s fingerprints were on a couple of the bottles; and, each of the wicks, when laid out on a table made the perfect pieces of a jig saw puzzle comprising a T-shirt. They found that the remnants of the T-shirt matched exactly other pieces found at McKenzie Red’s home. My understanding is that when confronted with this physical evidence Red plead guilty and was sentenced to five years in State Prison.
Evidence of origin and cause is the fire investigation aspect of the total investigation. Where did the fire start and what started the fire. This is based on fire science and the scientific documentation and examination of the characteristics of the fire being investigated. The evidence leading to the origin of the fire has to be thoroughly documented and prepared in a manner suitable for presentation in court.
Examine the scene from the areas of least damage to the areas of highest damage and destruction. The investigator's job is to look at the entire scene, both inside and outside the fire location. Investigators should always work in teams for more than one reason. The best reason is safety. There will always be someone there to call for help if the other is injured or needs assistance. When arriving at a scene have a plan. One investigator should work inside the building, one on the outside. On the outside the investigator should check for evidence of breaking and entering, tool marks, broken windows, footprints, utilities (on or off), smoke patterns, fire patterns, discarded evidence such as rags, combustibles or accelerant containers, talk to witnesses, policemen, firemen, etc. A good thorough examination of the outside of a fire scene may answer questions that the inside cannot.
Inside, I’ll say it again, work from the areas of least damage to the areas of highest damage and destruction. Examination of the scene creates questions in the investigator's mind. The investigator must work through those questions. Do a preliminary (or quick) check first to see any areas that offer revealing information. Use your nose, what is the odor inside the fire scene, any evidence of hydrocarbon substances, paint, etc. What is stored in the facility and is the building stocked or furnished in a manner that you would expect from a like facility? After the quick look, examine the fire scene carefully thoroughly documenting the fire patterns, destruction, and any evidence. If necessary, collect evidence, do a fire reconstruction, stay on the scene until the scene can answer no more questions.
The investigator should ask him/herself the following questions at the fire scene where the cause is suspected to involve the use of an accelerant. What does the scene smell like? What did the witnesses say about how the fire became visible? What did the first firemen and policemen at the scene see and smell? Are there other suspicious fires in the area that are being investigated? Did the burn pattern show an accelerant? Were there irregular shaped patterns on the floor or carpet? Was there a trailer evident? Where did the burn pattern show an accelerant? Where does knowledge of the way fire behaves indicate that traces of an accelerant most likely would still remain? Most poured accelerants remain at the circumference of the poured area. The best place to find residual accelerant traces, then, is the location at which the burned and unburned areas meet. Is there heavier charring in the area where the suspected origin is, something that would indicate soaked accelerants?
In determining the optimum location for residual accelerant, review the requirements for combustion: fuel, oxygen and an ignition source. The most important of these is oxygen. Because liquids can travel under places where air is limited, it is likely that you’ll have a better chance to find an accelerant residue under baseboards, at the out edges of carpet, beneath furniture legs with felt pads and under carpet tack strips.
Investigators lucky enough to arrive on the fire scene within two or three days of the blaze have with them the best and most sensitive piece of equipment: the nose. The nose is very sensitive to aromatic hydrocarbons. Combine sight and smell to aid in the evaluation of your prospective sampling site.
When an insurance fire claim has been denied, there is usually an analytical laboratory test report that forms at least the partial basis for that denial. It is very important for the defendant and plaintiff to make sure that the physical evidence supports the allegation that an accelerant was used. So don’t look only at those areas where you think an accelerant might have been used. To compile the most accurate picture of what actually occurred, consider all of the information the fire scene has to offer, but remember, lab results can, on rare occasions, steer the investigator in the wrong direction.
It is extremely important that the arson investigator understand what the potential of his investigation is. If he alleges accelerant was used and substantiates it through a lab examination and then points the finger at the homeowner or business owner, it is likely that the insurance company will not pay, whether or not there is a prosecution. This involves what is called the “burden of proof”. There are different burdens of proof in civil and criminal cases. Criminally, the charge of arson has to be proved beyond a reasonable doubt. If the insurance company refuses to pay, the owner has no recourse other than to sue the insurance company. The burden of proof in civil court is a “preponderance of evidence.” All this means is that the insurance company has to prove is that “more likely than not” the owner burned the property. You can see the advantage here. In conclusion, if the investigator carelessly points the finger at what he/she “thinks” might be arson, it could have dire consequences on an innocent homeowner.
It is also important to know that the homeowner does have recourse against a recalcitrant insurance company. There is a concept in the law known as bad faith. Each insurance company has a responsibility to deal with their insureds in a fair and just manner. They have a responsibility to pay their claims in a timely manner, the jury instruction says “when they could have or should have.”
The reason there are so few successful criminal arson prosecutions “only about 2 percent of set fires lead to convictions” (NFPA’s 2000 arson report) is that it is difficult to prove circumstantial cases against the arsonist. The arson investigator may have good analytical evidence of accelerant and good information on motive but the successful prosecution usually hinges on a circumstantial case. “All evidence of an indirect nature, It means that existence of principal facts is only inferred from circumstances.” (Blacks Law Dictionary). The principal fact “who done it” has to be inferred, or a logical conclusion of the evidence. The house burned, the investigator found evidence of accelerant and arson, the suspect had money problems, and the suspect was seen buying a three-gallon can of gasoline hours before the fire was set. These facts infer that the suspect committed the crime but offer no direct evidence. Direct evidence would be an eyewitness, suspect’s fingerprints on the accelerant bottle, a statement to another that he had burned the building. (Kirk’s 423).
The arson investigator must be aware that if he makes a mistake pointing the finger at someone that that can cause irreparable damage to the suspect both financially and emotionally. Here are a couple examples of successful challenges:
Phil Foster, an experienced arson investigator and educator, recently participated in the defense of a woman whose house had burned as the result of a lightning strike. They presented sufficient testimony from neighbors, fire department run reports and firefighters, and physical evidence in the outside electrical box and internal wiring to establish that a lightning strike was the cause of the fire to her house. The insurance company denied the claim based on a positive test result for an accelerant in the utility room area. The physical evidence Phil saw at the scene did not indicate that any accelerant had been used. Their problem was how to attack the sample.
The insurance company’s expert had testified in depositions that the area of origin was in a very small utility room in the south part of the home. He stated there was a small amount of an accelerant poured between an outside door and the front of the washer and dryer. He also stated he had taken another sample from around the corner in the kitchen that did not show accelerant residue.
Upon reviewing the photographs taken from the initial visit before the depositions, it was obvious that the burn patterns the expert had identified in his photographs were in fact burn patterns on the 12 inch vinyl flooring from falldown (burning pieces of ceiling materials). There were similar patterns throughout the home. All indicated falldown from burning ceiling joists and hot shingles.
The homeowner had already told the insurance investigator there were no accelerants, such as lawnmowers, or gasoline cans, in the utility room. The insurance company’s expert went on to state that he was sure this pour pattern in front of the washer and dryer was where the gasoline was poured because there was what appeared to be evidence of spalling—breaking up of the concrete caused by extremely high temperatures—on the concrete floor.
The expert was then shown his own photographs of spalling of the concrete pad under the carport, which had occurred when hot asphalt shingles had fallen down in the parking area. He said he’d at first thought an accelerant had been poured there as well, but realized it was spalling due to hot shingle fall down. He had no answer as to why if this condition could occur on one piece of concrete it couldn’t have occurred on another.
Thus, the investigator must coordinate his investigation, photographs and sample taking. Anticipate their possible use at a deposition so you can neutralize whatever theory the defense develops. Before an arson investigator files charges against an individual he must be assured that that person is the one that committed the crime. The thought, “well, its up to a jury” does not cut it. You are responsible and must be sure that you are following the right path. Do not accept pressure from supervisors, chiefs, prosecutors or family members to file charges. This is a personal decision, if the evidence is there, do it, otherwise, keep working until you either can give no other cause than unknown, clear the individual or have sufficient evidence for conviction.
Without other evidence to support it, a positive test doesn’t necessarily indicate that an accelerant was used and for sure doesn’t indicate that the homeowner did it. This is important when considering charges, or when considering the denial of a claim by an insurance company. Many insurance companies will deny a claim solely on the basis of a positive test result.
NFPA 921 gives many instances where the assumption “used to be arson” if certain physical evidence was found. The manual is clear that the investigator has to be careful in making these assumptions. There is an exception to nearly every one of these hard and fast arson indicators. Read carefully and be thorough. Don’t jump to conclusions.
An arson investigator must also remember that what he says and what he writes will be closely scrutinized by the insurance company and later the attorney for the homeowner if the claim is denied.
While physical evidence supported by lab tests is essential in arson cases, it is also important to understand these tests and how they may identify accelerants. An integral part of this knowledge is how to properly collect, catalog and preserve evidence.
Many private laboratories will process arson evidence while most states have State Police or Fire College Laboratories. These labs may also do private cases on their own time for a set fee. The investigators best course of action is to call the lab that he intends to use and find out how the lab wants the evidence collected, packaged and sent.
Make sure on the lab test request that a fuse or rag submitted to the lab for testing is not destroyed in the process of testing. The previous example of the T-shirt rag fuses is a good reminder that everything is evidence. In a personal-injury case involving an electrician, the client, wearing freshly washed blue jeans, was engulfed in flames when he attached test probes to a 440-volt, three phase box. The resulting flash was very unlike an electrical fire. A test of the jeans determined hydrocarbon residue on the front thigh but not the rear. This indicated some type of hydrocarbon-based material was present and was probably used to clean the contacts on the switch prior to the electrician’s arrival.
It is important to seal the sample and preserve the accelerant. Don’t use plastic bags, paper bags or boxes. Employ unused, unlined gallon-size paint cans to submit evidence (lined cans have a mineral spirit base that will register on the sensitive test instruments.) All auto paint stores sell these cans at a reasonable price. Buy 10 or so and keep them in a closet, in a new, clean, cardboard box, in the office. But don’t store the empty clean containers in the vicinity of any actual evidence stored. Be on the lookout for cross contamination at all times. NFPA now permits the use of glass jars as well. Advantages and disadvantages of cans and jars are: when using cans you cannot see the evidence without opening the can: jars can break and are not usually big enough for large samples of material. (make sure that there is no rubber seal on the top, that will interfere with your sample).
The process of opening the can after it is sealed releases gases that have been stored. Regardless of what container you use, store them in a way where they are not contaminated from other sources. If you keep them in the trunk of your car around tools and other equipment the defense can accuse you of spoilage of the containers by contamination from other sources. Use a method of storage and transportation that keeps the cans or jars clean, unused and separated from any other contamination. On the same subject, don’t contaminate one sample with another. Use different plastic gloves when handling each sample or use clean tongs to place evidence in containers.
The size of the sample need not be huge; a half a can or jar per area or less. After placing the sample in the can, turn the can upside down and step on it to insure that it is sealed and the vapors will not escape. Don’t put water in the container; it may evaporate. Jars and cans should be sealed with evidence tape to guarantee that there has been no tampering.
When taking a sample of flooring or material from a suspected origination point, take the sample most likely to produce results, even if you have to cut it out with an ax. Use one sample from one area at a time. You may need samples from several areas if there are suspected multiple starting points. Keep these in separate, individually marked cans.
This is an overview of the process so be careful to note that the NFPA 921 methods and procedures are the ones that should take precedence.
After sealing, on both the lid and the side of the can, write a description of the sample and a number. Initial and date each can and seal with evidence tape to ensure chain of custody. On this you should include:
· An itemized list of the evidence being submitted with information concerning the means by which it is being forwarded.
· The date and time of burning.
· A brief description of the type and construction of the burned building or object and the extent of damage or destruction caused by the fire.
· A list of the chemical agents used in extinguishing the fire. (Water, carbon tetrachloride and carbon dioxide are the most common agents.)
· Photographs and scaled sketches on which are indicated the points where the various articles of evidence were collected.
Before packaging, the evidence for mailing or hand-delivery to the laboratory, prepare a letter of transmittal, relating the sample number, a description of the sample and from where it was removed in the fire. Example: #1—Piece of carpet taken from N.W. bedroom under window #2 (as indicated on the attached sketch).
(From O’Hara’s Fundamental’s of Criminal Investigation, fourth edition)
When the lab receives the evidence package (send it certified or registered-chain of custody or Overnight (signature required), the chemist will write on the package the time and date and in what manner the package was received. A laboratory number will be assigned and written on the lid and the side of the can.
All these procedures are designed to obtain a sample that can be analyzed on a gas chromatograph. (Labs also use this instrument to run blood alcohol tests and to do drug analysis.) The Chemist injects a sample of an unknown; the machine analyzes it and prints out a graph of an absorption spectrum. A chemist compares the graph to absorption spectra of known materials to identify the unknown. (Kirk’s p336).
Gas Chromatography/mass spectrometry (GC/MS) Mass Spectrometry allows the analyst to break apart each compound into small submolecular pieces and, by counting those pieces, establish the chemical structure of the original molecule. (Kirk’s 339).
The chemist who removes a sample from the can for examination is concerned with a vapor rather than an actual piece of the evidence. There are many methods of vapor extraction, or removal, of the accelerant from the sample, four of them are liquid, steam distillation, solvent wash and headspace. (Read Kirk’s starting on p. 340 for details).
The most preferable of the methods available is the use of a liquid, such as that residual liquid found in an unbroken Molotov cocktail or in a gasoline can containing the remains of the flammable liquid used in the initiation of a fire. This type of sample is transferred to an airtight container and subsequently examined.
Pure liquid is the best source of material for identifying flammable liquids and comparing questioned material with known standards. A very small quantity of material is needed and very little time is utilized because instrument programs can be preset, thereby eliminating the necessity for repeating runs with adjustments to the instrument.
Many types of materials can be prepared for analysis by steam distillation. These items frequently possess readily detectable odors, indicating that an adequate quantity of material is available for recovery by distillation. These items include fragments of wood, soil, drapery and carpeting.
Steam distillation works on the principle that a petroleum-based flammable liquid is insoluble in water, lighter than water and will float on the top of the water that has been condensed from steam. With a pipette, the chemist removes a small amount of the liquid floating on the water and puts it in a flame. If it burns, it proves a flammable liquid is involved.
This method is ideal in recovering quantities of accelerant from plastics, rubber goods, resinous materials and others that either absorb or dissolve in flammable accelerants. However, this procedure is limited in recovering accelerants from mixtures of foaming agents, such as soaps. (These items are frequently encountered in sabotage cases and incendiary devices). Also, items to be examined must necessarily be suitable for partial destruction, since fingerprints are lost, shrinkage frequently occurs, and other changes related to immersion in hot water are seen.
Hardwood, porcelain, glass, metals and similar hard-surfaced items lend themselves to the solvent-wash technique. Usually, no odors can be detected in these materials, and indications are that a very small quantity of only the high-boiling fractions of an accelerant remains for recovery.
After placing the specimen in a suitable container for washing, the item is washed several times in a solvent, such as hexane. Virtually all of the fractions of an accelerant present can be recovered from arson debris in this manner, and the quantity can be concentrated by a careful evaporation of the solvent to a small quantity.
The headspace method is the most common method of processing evidence for accelerants. It requires just the heating of the can of evidence and then extracting vapor from the top by means of a gas syringe. This sample is then injected into the gas chromatograph for analysis. This preserves the evidence and does not allow contamination of the sample. If the investigator needs the items of evidence back intact, specify the headspace method.
Headspace collection often recovers samples from specimens that cannot be treated by the other methods. Such specimens include items of clothing that cannot be altered or destroyed; leather goods; canvas; items of fabric; specimens contaminated with foaming agents, such as soap; and absorbent plastics and rubber. A group of items, such as pieces of clothing or several documents, can be handled at one time without destroying fingerprints, writing or other aspects of forensic interest.
In most cases of miss-handled evidence, the investigator has fouled up. Numerous problems are encountered in the recovery of accelerant materials form submitted specimens. These problems limited the potential identification of accelerants, often result from the lack of care the investigator takes in collecting and handling the specimens.
Many specimens the investigator obtains simply aren’t appropriate. Rather than submitting a piece of drapery or carpeting, which are highly absorbent, an investigator may take pieces of glass, ceramics or similar small, hard-surfaced, non-absorbent materials. These breed limited success.
Furthermore, the investigator may encounter difficulty with many specimens because of the absence of accelerant or because of the type of material itself. For example, in a heavily charred wood, all flammable accelerant may have been lost. Or, the investigator might submit a rag that was soaked in the water the fire department used to extinguish the blaze and had dried out. Then, there’s a soap sample recovered near the site of origin. Because of interference due to foaming, analysis of the soap for an accelerant would exclude the solvent-wash recovery method as well as any other method that might cause interference.
One more item to make a note of. When taking samples for lab examination, take exemplar samples as well. If you suspect accelerant residue in a piece of carpeting, take a sample of unburned carpet and place it in a separate container for examination. Burning of the unburned sample will confirm or deny the presence of petroleum byproduct from the particular carpet sample. When using a piece of alloyed or melted metals, as evidence of heat, take a sample of the unburned metal for the lab to heat for use as a constant. Remember to think of these investigations in scientific terms, make sure that you can prove and provide adequate, confirmed facts to prove your hypothesis.
In summary, a timely investigation of the fire scene, careful observation with a photographic record, prudent sample site selection and careful preservation of sample and their chain of custody will go a long way toward establishing the cause of the fire and the presence or absence of criminal activity.
Article updates written by James W. Harbert CLI, FCI, based on a prior article published in “The Legal Investigator” by James W. Harbert and Phil Foster. Phil Foster is a trained arson investigator who has worked privately since 1983. Phil has contributed research, photographs and material to this course and continues to advise and review the finished product @James W. Harbert, February 2001.