ARSON & SABOTAGE ROLE OF FORENSIC SCIENCE IN INVESTIGATION

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INTRODUCTION

1.??????????????Damage from the fire is World's most costly public safety problem. Losses due to fire, in life, and injury, are exceeded only by those due to traffic accidents. The cost of fire damage to the World community has been estimated to be millions per year. Our own experience over recent years suggests that this may be a conservative estimate. Arson, the willful and malicious burning of property, accounts for approximately 30 percent of this figure.

2.??????????????The most effective way to try and reduce this appalling cost, and to reduce the damage caused by fire, is effective fire investigation. It should then be possible to reduce the number of accidental fires by improving building codes, and by identifying and eliminating dangerous products. Arson is said to be the easiest crime to commit (even young children can do it), but the most difficult to detect and prove. It needs to be combated by finding and prosecuting those responsible.

FIRE INVESTIGATION

3.??????????????A fire investigation is an unenviable task. The devastation, charred debris, collapsed structures, and water-soaked ashes, together with the smoke and stench, make the task uninviting and seemingly impossible. In the past many investigators appear to have come to the task with inherent biases; fire brigade members have decided that all unexplained fires were due to electrical faults, whilst police and insurance investigators leaned towards "arson, by a person or persons unknown".

4.????????There are different types of fires; in homes or factories, in the bush, or in a forest. The best investigation would use a team of trained personnel; fire brigade staff, with their experience of fires first-hand, and police and insurance investigators, with their skills for determining motive and opportunities. An electrical engineer or electrician is required to investigate electrical systems. The scientist also has a most valuable role to play. The scientist should be able to arrive at a fire scene without any predetermined ideas. An analytical approach, using patient, thorough, and systematic techniques should reveal critical and vital information. The knowledge of a chemist is invaluable. A chemist should understand the properties of fuels and building materials and have an understanding of the combustion process. In addition, an analytical chemist should also be able to identify the laboratory materials found at the fire scene, even if they are only present as trace amounts.

METHODOLOGY

5.??????????????The basic role of an investigator at a fire scene is twofold; firstly to determine the origin of the fire (the site where the fire began), and secondly to examine closely the site of origin to try and determine what it was that caused a fire to start at or around that location. An examination would typically begin by trying to gain an overall impression of the site and the fire damage; this could be done at ground level or from an elevated position. From this one might proceed to an examination of the materials present, the fuel load, and the state of the debris at various places. The search for the fire's origin should be based on elementary rules such as:·

• Fire tends to burn upwards and outwards (look for V-patterns along walls).
• The presence of combustible materials will increase the intensity and extent of the fire; the fire will rise faster as it gets hotter (look for different temperature conditions).
• The fire needs fuel and oxygen to continue.
• A fire's spread will be influenced by factors such as air currents, walls, and stairways. Falling burning debris and the effect of fire-fighters will also have an influence.

6.??????????????Knowledge of the color and state of various materials at elevated temperatures is required to help determine the temperature of the fire in different locations. An examination is also carried out of structural deformations, char depths, and smoke patterns. It is important to try and discover if the fire started at floor level, as from a cigarette butt, or at an elevated level, as for a gas explosion. This summary attempts only to indicate some of the steps typically undertaken. A more detailed list can be obtained from a number of texts.

7.??????????????These procedures are designed to locate the site of origin of the fire. Multiple sites of origin suggest a deliberately lit fire. Assuming that the site of origin has been found a thorough examination of the debris in this area is then necessary. All electrical appliances in the vicinity should be examined. The presence of any flammable liquids, trails, spalling of concrete, or intense burn marks on the floor should be checked. No fire can commence without an ignition source. One should therefore be on the lookout for matches, lighters, sources of sparks, hot objects, chemicals, gas, and electrical lines, cigarettes, fireplaces, and chimneys.

8.??????????????A knowledge of spontaneous combustion, and its likely sources, is needed. It may be necessary to collect samples and carry out experiments in the laboratory (it is not difficult to show that loose rags with linseed oil on them cause spontaneous combustion). The collection of samples requires a chemist's knowledge of sampling procedures and the need to obtain uncontaminated materials.

9.??????????????Provided the investigation has been patiently and scientifically carried out, when combined with the evidence of eyewitnesses or fire officers, it may be possible at this stage to draw a conclusion about the fire. Typical causes of accidental fires are cooking accidents, overheated or short-circuited electrical connections, spontaneous combustion of oils, welding sparks, burst gas lines, sparks from fireplaces, lightning, cigarette butts, and left-on appliances, and reacting chemicals. The list of all the possible causes is very long.

ARSON

10.???????????If a fire is not the result of an accident, it must have been deliberately lit; arson. The motives to commit arson include vandalism, fraud, revenge, sabotage, and pyromania. A major objective in any suspected case of arson would be to search for, locate, sample, and analyze residual accelerants. Most, though certainly, not all incendiary fires involve the use of an accelerant to speed the ignition and rate of spread of fire. A rapid and intense fire, inconsistent with the natural fuel loading is indicative of an accelerated fire. Such a fire is likely to be initiated at ground level, possibly in a number of sites, and may produce trail marks, burn-throughs, or spalling of concrete.

11.???????????The accelerants most commonly used, on account of their flammability and ready availability are petrol, kerosene, mineral turpentine, and diesel. Other accelerants such as alcohols, acetone, and industrial solvents are less commonly used. It might be thought (certainly many arsonists assume) that after an intense fire there will be negligible amounts of such accelerants remaining. Given our current sophistication of analytical techniques, this is not true. The amount of accelerant remaining after a fire will depend on factors such as the quantity and type of compound used, but also on the nature of the material it is poured on, the elapsed time since the fire, and the severity of the fire. Chemists have been able to locate and detect trace amounts of liquid hydrocarbons in the soil beneath a gutted house several months after a fire.

12.???????????Detection of trace quantities of materials requires careful attention to sampling techniques and analysis. The most frequently sampled material is flooring material such as wood, carpet, soil, and linoleum. A porous material is best. There is a need to take control samples in some cases, away from the area where the accelerant is suspected, but preferably of the same material as the sample.

13.???????????Some investigators use "sniffers" at fire scenes. These portable detectors usually note changes in oxygen level on a semiconductor. They are not specific for liquid hydrocarbons, respond to a variety of vapors, and need to be used with caution. They can be used as a guide as to the best place from which to collect samples, for removal, and analysis in, the chemical laboratory.

SAMPLING

14.???????????The materials found to give the most positive analyses for accelerants are porous samples; carpet and underlay, cardboard, paper, felt, cloth and soil. At all stages, because of the sensitivity of the analysis, care must be taken to avoid contamination. In our experience, unlined metal cans have been found to be the best containers.

15.???????????Lined cans may have a coating that contains volatile components and should not be used. Plastic bags may allow diffusion of volatile components either into or out of the sample and are not recommended. Glass containers may be used, but the cleanliness of lids needs to be assured. Can need to be clean and well-sealed and clearly labeled, for transport to the laboratory. At the laboratory, they need to be documented and kept secure prior to analysis.

EXTRACTION

16.???????????The methods of extraction most commonly used for fire debris samples are distillation, solvent extraction, and headspace analysis. The distillation techniques used have included steam distillation, ethylene glycol distillation, ethanol distillation, and vacuum distillation. Of these, steam distillation has been the most widely used, and is still used, particularly where reasonably large quantities of accelerant are suspected to be present. Solvent extraction is not used except in special cases. Both static and dynamic headspace analysis are now in common use, in both cases at and above room temperatures. In the former case, a needle of a gas syringe is placed into a container containing fire debris, and a volume of vapor is withdrawn for analysis.

17.???????????Our own preferred method, on the basis of experience and experimentation, is for dynamic headspace extraction, as represented in the Figure above. The fire debris, in its original container, is placed into an oven and heated at 150° C for approximately one hour, whilst at the same time a continuous flow of filtered nitrogen gas flushes the headspace and sweeps any volatile components through a water trap onto an absorbent. This method in effect samples 3000 times more gas than does a static headspace sample. It has the advantage that the can is always vented so that pressure does not build up in the can. Water present will volatilize, and essentially steam distills the sample.

ABSORPTION AND DESORPTION

18.???????????The absorbents in most common use are activated charcoal, Tenax G.C., and Porapak Q. All three use absorb accelerant components but do not absorb water or nitrogen. Tenax is stable up to 350C and is ideal for rapid thermal desorption. It is used for most fire samples by the London Metropolitan Police Laboratories (Scotland Yard). An advantage of thermal desorption is that the material to be analyzed can proceed directly from the absorbent into a gas chromatogram. One disadvantage is that when this happens the sample is used up, and the evidence is no longer present.

19.???????????In the case of solvent desorption one obtains a liquid sample that can be re-analyzed many times and retained as evidence. A variety of solvents have been used for desorption, but we have found carbon disulfide to be the best, because of its high desorption efficiency for the components commonly found, its low detector response, and its high volatility. We use 1 ml A.R. grade carbon disulfide for extraction, and store liquid samples in a glass vial to which we add 1 ml water to prevent loss by evaporation.

DETECTION AND IDENTIFICATION

20.???????????Ultraviolet, infrared, and nuclear magnetic resonance spectroscopy have all been used for identifying accelerant components, but by far the most widely used technique is gas-liquid chromatography. It is able to separate and detect trace amounts of volatile hydrocarbons in complex mixtures. The flame ionization detector has been widely used because of its great sensitivity to these components. The introduction of capillary columns allows for smaller samples and produces sharper peaks and greater resolution. The number of different columns now available is quite large, but we have found that a 25m. BP-1 capillary column, 0.33mm. i.d. to be widely applicable. In our laboratory, we run unknown samples on a dual plotter against standard samples, so that a comparison can be made of samples run under similar conditions.

21.???????????The four most commonly found accelerants (petrol, kerosene, mineral turpentine, and diesel) are all highly complex mixtures of many components, in very different ratios. Most forensic laboratories feel confident in identifying these compounds on the basis of their gas chromatograms alone, even if the samples are evaporated and contaminated.

22.???????????In order to make a positive identification it is necessary to identify a large number of the components present, and to note that their ratios are very similar to that of a standard. The use of evaporated and burnt standards may aid this comparison. To make absolutely sure of the identity of any component we have relied on gas chromatography/mass spectrometry (GC/MS). We have been fortunate to have available an AEI MS902, fitted with a Pye Unicam GC, and more recently a Hewlett Packard GC/MS, the 5970 MSD. This latter instrument contains a data library of some 42,000 compounds. It is possible to conduct searches for particular fragments, groups of fragments, or molecular ions and is particularly well suited to identify aliphatic and aromatic hydrocarbon peaks and mixtures.

23.???????????We have had a number of honors students working on finding the best experimental conditions, and on identifying as many as possible of the straight and branched-chain aliphatic hydrocarbons, the xylenes, tri and tetramethyl benzenes, naphthalene, and methyl naphthalenes, styrene, and indanes. In the case of petrol, it is also possible to detect and identify, under different conditions, the organo-lead additives. At the same time consideration has also been given to the effects of evaporating and burning accelerants. A study has also been made on likely contaminants, particularly the pyrolysis products from various plastics, carpets, wood, tiles, glues and other adhesives, lacquers, thinners, and vegetable oils. We have built up a library of possible contaminants. The techniques described are capable of detecting 1 uL of accelerant. In fact, it is possible to detect 0.1 uL, but we have set a minimum level of 1 uL, because of the possibility of background material that may be present. At this level, one must be very careful about contamination and pyrolysis compounds, so that they are not confused with accelerants. It is necessary to clean all equipment before use and to run blanks at regular intervals to ensure that there is no contamination present.

CONCLUSION

24.???????????Fires present a major social and economic problem. A thorough investigation of any large-scale fire is it accidental or deliberate, is warranted. Chemists have expertise that can be used in an on-the-spot investigation, and in the analytical laboratory. This is not an area for which many scientists in Australia have been specifically trained but is an area where the chemist's skills and expertise can be of great benefit.

SAMPLING DEBRIS AT THE FIRE SCENE

INTRODUCTION

1.??????????????One of the many objectives of a fire cause and origin investigation is to determine whether flammable liquids were deliberately used to accelerate the spread of the fire. These liquids are termed accelerants and if their use is suspected at the fire scene then debris samples from various areas should be submitted to the laboratory to determine the presence, distribution, and identity of the accelerant. This information will support the investigator's own understanding of the ignition and propagation of the fire.

?2.??????????????The efforts of the forensic laboratory are entirely dependent on the quality of the samples provided and therefore a major objective in forensic fire cause determination is to successfully locate and sample fire debris for subsequent laboratory analysis for residual accelerants. To achieve this aim the investigator needs to apply the proper sampling techniques and have a basic understanding of the chemical and physical nature of some of the common accelerants and their behavior during and after a fire. The aim of this paper is to briefly explain some of these considerations.

THE NATURE OF ACCELERANTS

3.??????????????The most commonly used accelerants are petrol, kerosene, diesel, and mineral turpentine. They are all derived from crude oil which is a very complex mixture of hydrocarbons whose components with similar physical and chemical properties are collected to give the various fuels and solvents. Because the common accelerants are themselves complex mixtures it is best to examine the graphs produced from the analysis by Capillary Gas-Liquid Chromatography (GLC) to understand their properties and behavior.

?4.??????????????Gas-Liquid Chromatography is the most widely used laboratory instrument for analyzing accelerants because of its ability to detect and identify trace amounts. A headspace or liquid sample of the volatiles extracted from the fire debris is taken and introduced into the instrument where it is volatilized and swept by a gas stream through a long tubular column towards a detector. As the sample moves through the column the various components will separate so that the compound with the lowest boiling point will emerge from the column first to be detected followed by the other components in order of their boiling points. By measuring the time from injection at which the individual components emerge from the column it is possible to positively identify each component. The entire analysis is recorded on a chart called a chromatogram where each component of the sample is represented by a peak and the overall pattern is essentially a fingerprint for each accelerant.

5.??????????????Figure 1?shows the chromatograms produced from the analysis of fresh, kerosene, fresh diesel, and evaporated kerosene exposed to the atmosphere for seven days. The major peaks in the chromatogram are labeled according to the chain length of the molecule producing the peak.

?6.??????????????By comparing the chromatogram produced from fresh kerosene and diesel it can be seen they have similar components and are complex mixtures being produced from the fractional distillation of crude oil. Diesel is however composed of components that have a higher boiling point and so are termed a heavier fraction. As kerosene weathers, the more volatile components tend to evaporate and its chromatogram begins to resemble that of diesel. For this reason, it is difficult for an analyst to conclusively identify kerosene in fire debris samples if sampling is made sometime after the fire and weathering of the accelerant has occurred.

?7.??????????????Petrol is a more volatile mixture than kerosene and therefore more readily forms explosive mixtures in the air which upon ignition can cause considerable damage to the surrounding environment. The chromatograms produced from the analysis of fresh petrol and evaporated petrol are shown in?figure 2?and it can be seen there are fewer peaks present in the chromatogram of evaporated petrol. The analyst when presented with this chromatogram being essentially a partial fingerprint of the accelerant has less information with which a conclusion can be made regarding the identification of the accelerant.

?8.??????????????The common accelerants are all insoluble in water and as such are not readily washed away during the extinguishing of the fire. They tended to become sealed into porous surfaces which prevent their evaporation and have been found to remain at the fire scene for periods of up to three months. Water-soluble accelerants such as methylated spirits, acetone, and some industrial solvents tend to be washed away from the fire scene. Traces do remain but will readily evaporate because they are not sealed into the surfaces by water. If a water-soluble accelerant is suspected in a debris sample the analyst should be notified in case the analytical procedures require some modifications to successfully analyze water-soluble compounds.

?9.??????????????Because of the reasons illustrated above it is important to sample debris as soon as possible after the fire so the laboratory analysis will yield as much data as possible on which to base a conclusion regarding the presence and identity of an accelerant.

WHERE TO SAMPLE

10.???????????At the fire scene various indicators are used to predict the presence and location of an accelerant. These may be eyewitness reports of a raid and intense fire in its initial stages or the presence of heavily localized burning to the flooring material and overhead damage which is inconsistent with the combustion of the naturally available fuel below. Accelerants are normally found at the area of origin of the fire, in doorways where an arsonist would attempt to leave a building, and in large spaces such as in the center of a room where the arsonist can move about freely when distributing the accelerant. It is often helpful when attempting to locate areas where accelerants may be present to visualize the scene before the fire and predict the movements and actions an arsonist would make whilst spreading an accelerant.

MATERIALS FOR SAMPLING

11.???????????After locating the area where it is felt an accelerant may be present a sample of debris that will have the highest probability of retaining traces of accelerant is required. As general rules, if the area to be sampled is wet traces of petroleum derive accelerant would be expected to remain. Therefore the best materials to sample are wet porous materials such as soil, paper, cardboard, bagging, carpet, cloth, and to a lesser extent concrete. Readily combustible materials such as rubber and timber are generally not good materials to sample because their combustion supports the depletion of the accelerant.

?12.???????????When sampling a material that is difficult to remove such as concrete, an absorbent may be sprinkled onto the surface to absorb water, and in turn traces of an accelerant if present and the absorbent recovered and analyzed. Absorbents that can be used are diatomaceous earth which is commonly used for swimming pool filtration, fuller’s earth, inorganic carbonates, and some industrial absorbents. Flour has been used but is unsatisfactory because its subsequent fermentation in the container will produce ethanol which is the major component of methylated spirits. Household absorbents such as sanitary napkins and disposable nappies can also be used to sample from concrete.

?13.???????????To assist in the selection of a sample the investigator normally uses their own sense of smell to detect any odors of accelerants. The debris can be smelt directly or warmed in one's hands to release vapors. The use of portable gas detectors (Sniffers) at the fire scene to detect traces of accelerants has also been used.

?USE OF A SNIFFER

14.???????????Various types of sniffers are manufactured and are best classified according to the principle of operation of their detector. They may employ a flame ionization detector or a catalytic oxidation probe. The latter is the most commonly used because of its low cost and robust design. The major problem when using nearly all types of sniffers regardless of their principle of operation and their price is they cannot discern between accelerant vapors and pyrolysis products and because of this their use at a fire scene remains a continual source of controversy amongst investigators.

?15.???????????The main advantage when using a sniffer rather than relying on one's sense of smell are:

·???????The sense of smell varies widely amongst individuals both qualitatively and quantitatively and tends to deteriorate during the day particularly if noxious gases are present.

·???????From a safety point of view, it is not good practice to regularly smell fire debris as toxic pyrolysis products are present at all fire scenes.

·???????The sniffer probe can be inserted into difficult areas to reach such as under freshly lifted carpet or into drainage pipes.

·???????They are invaluable when tracing the source of a readily dispersible vapor such as a gas leak.

16.???????????The materials that gave the highest ratio of true positive readings were carpet, cardboard, paper, felt, and cloth. The investigator when using a sniffer should sample these materials if an option exists. The soil sample gave the highest ratio of false-negative readings (8 out of 12) indicating that when testing on-site the soil must be freshly disturbed so that accelerant vapors are released to be detected. The high overall number of false-positive readings obtained (20 out of 63) using the sniffer indicates the lack of specificity of the instrument.

?17.???????????For testing materials such as rubber-backed carpet or polystyrene which can both produce liberal amounts of pyrolysis products as indicated by their odors, the sniffer will give random positive readings that could confuse the operator. Also, a poorly tuned instrument, a low battery, or an instrument malfunction may give the investigator a false impression that accelerants are absent from the fire scene.

?18.???????????Sniffers can be a valuable aid at the fire scene however the operator must be aware of the principle of operation of the instrument so that it may be tuned correctly before use and its results are interpreted correctly. It must be stressed they are only to be used as an aid for the collection of samples for laboratory submission and their results are not conclusive regarding the presence or absence of an accelerant. The best option for selecting debris samples is to use a combination of relying on one's sense of smell and having a sniffer on hand to use as the circumstance requires.

?SAMPLING CONTAINERS TO USE

19.???????????Various containers have been used for sampling fire debris however unlined metal paint cans are regarded as the most suitable because of their excellent sealing capabilities, their robust design, and are harmonious with most analytical techniques. Plastic bags are easily pierced and are prone to the diffusion of vapors both into and out of the bag and glass jars are fragile.

?20.???????????Metal paint cans come in a variety of sizes and types being unlined or lined with an epoxy coating designed for the storage of water-based paints.?Figure 3?is a chromatogram produced from analyzing the volatiles extracted from a lined can together with a chromatogram of petrol. It can be seen an industrial solvent, similar to petrol has been used in the manufacture of the lining, and for this reason, lined cans should never be used for sampling fire debris.

CONTROL SAMPLES

21.???????????Control samples or blanks generally form part of the scientific process to ensure that background materials do not contribute to the result.

GUIDE FOR INVESTIGATING FIRE AND ARSON

1.??????????????Fires are destructive, spreading as they grow and consuming the evidence of their initiation. Putting out fires and finding out how they started involves public officials and private groups — such as fire departments, emergency medical services, and law enforcement. Law enforcement and fire service departments must always determine the cause of the fire, whether arson or accidental, in order to identify hazards and dangerous practices and prevent future fires. Many fires can be prevented through public education — for instance, educating people on safe practices for using room heaters or other gas and electric devices.

2.??????????????Not every portion of this document may be applicable to all fires. It is at the discretion of responding personnel (depending on their responsibilities, as well as the purpose and scope of their duties) to apply the procedures recommended in this Guide to a particular incident. Some of the procedures described in this Guide may not be performed in the sequence described or may be performed simultaneously.

ARRIVING AT THE FIRE AND/OR ARSON SCENE

First responders?to a fire scene must assess and secure the scene and ensure that victims receive medical attention.

• Observe the fire and scene conditions.
• Exercise scene safety.
• Preserve the fire scene.
• Establish security and control.
• Coordinate interagency activities.

OBSERVE THE FIRE AND SCENE CONDITIONS

First responders at a fire scene must observe conditions and activities and provide investigators with an accurate and complete description.

While approaching a fire scene, first responders should observe and mentally note the following conditions and activities and initiate permanent documentation of the information (e.g., written notes, voice recordings, and videotapes):

• The presence, location, and condition of victims and witnesses.
• Vehicles leaving the scene, bystanders, or unusual activities near the scene.
• Flame and smoke conditions (e.g., the volume of flames and smoke; the color, height, and location of the flames; the direction in which the flames and smoke are moving).
• The first public safety personnel to arrive on the scene, whether they are law enforcement professionals, firefighters, or emergency medical services (EMS) personnel.
• The type of occupancy and use of the structure (e.g., a residential occupancy being used as a business).
• Conditions of the structure (e.g., lights turned on; fire through the roof; walls standing; open, closed, or broken windows and doors).
• Conditions surrounding the scene (e.g., blocked driveways, debris, damage to other structures).
• Weather conditions.
• Unusual characteristics of the scene (e.g., the presence of containers, exterior burning or charring on the building, the absence of normal contents, unusual odors, fire trailers [physical trails of fuel and the burn patterns caused by those trails]).
• The fire suppression techniques used.
• The status of fire alarms, security alarms, and sprinklers.

EXERCISE SCENE SAFETY

Safety overrides all other concerns. First responders must make sure that victims, bystanders, and public safety personnel are safe. This involves mitigating safety hazards that may further threaten victims, bystanders, and public safety personnel. They must exercise due caution to avoid injuries to themselves and others.

First responders should:

• Evaluate the scene for safety hazards (e.g., structural collapse of the building; smoke; electrical, chemical, or biological hazards; other health risks).
• Establish safety/hazard zones.
• Communicate hazards to other personnel arriving at the scene.
• Use tools and?personal protective equipment?appropriate to the task during all operations.

DANGER: Beware of incendiary or explosive devices!?The scene may contain devices specifically designed to kill or maim public safety responders. Do not touch any suspected incendiary or explosive device. Evacuate the area, and request the services of personnel trained in the removal of such items.

PRESERVE THE FIRE SCENE

First responders must understand how rescue, medical, fire suppression, overhaul, and salvage efforts can adversely affect evidence and take steps to preserve it. They should secure the fire scene and identify potential evidence, take preliminary steps to preserve it, and notify appropriate authorities about its existence.

?First responders should:

• Observe and mentally note evidence at the scene, such as:
• Fire patterns (including multiple fire locations).
• Burn injuries to victims and fire patterns on clothing.
• Trailers, ignitable liquids, or other unusual fuel distribution (e.g., piles of newspapers and/or furniture pushed together).
• Incendiary/ignition/explosive devices (e.g., lighters, matches, and timing devices).
• Shoe prints and tire impressions.
• Broken windows and doors.
• Distribution of broken glass and debris.
• Indications of forced entry (tools and tool marks).
• Containers.
• Discarded clothing.
• Trace evidence?(e.g., hairs, fibers, fingerprints, blood, and other body fluids).
• Evidence of crimes in addition to the possible arson (e.g., weapons, bodies, drugs, and/or clandestine drug laboratory equipment).
• Witnesses, bystanders, and victims.
• Any other unusual items or the absence of normal contents or structural components.
• Recognize threats to evidence (i.e., its movement, removal,?contamination,?or destruction) from any of the following sources:
• Fire-suppression activities may wash away or dilute potential evidence.
• Overhaul activities that destroy fire patterns.
• Salvage activities that involve moving or removing physical evidence.
• Tool use that may destroy evidence.
• Moving knobs, switches, and controls on appliances and utilities.
• Weather conditions that affect?transient evidence?(i.e., wind, precipitation, or temperature changes).
• Personnel walking through the scene.
• Witnesses and victims leaving the scene.
• Medical intervention and treatment of victims (e.g., by damaging evidence at the scene or destroying victims' clothing).
• Premature removal or movement of bodies.
• Vehicles at the scene (e.g., that introduce fluid to the scene through vehicle leaks or destroy other evidence, including shoe prints and tire impressions).
• Contamination from external sources, such as fuel-powered tools or equipment.
• ?Protect evidence by:
• Limiting excessive fire suppression, overhaul, and salvage.
• Avoiding needless destruction of property.
• Leaving bodies undisturbed.
• Flagging items of evidence with cones or markers.
• Recording observations through written notes or voice recordings.
• Cover items or areas containing evidence with objects that will not contaminate the evidence (e.g., clean boxes or tarpaulins).
• Isolating items or areas containing evidence with rope, barrier tape, barricades, or sentries.
• Retaining and securing clothing items removed from victims and suspects.
• Obtaining information about victims and witnesses (i.e., their names, addresses, and telephone numbers).
• Preserving transient evidence (e.g., trace evidence, shoe prints, and tire impressions).
• Removing evidence if it might be destroyed by the fire or the collapse of a damaged building.
• Telling arriving investigators about what evidence has been discovered.

ESTABLISH SECURITY AND CONTROL?

First responders should immediately establish control of the scene and initiate documentation of the scene.

To establish security and control, first responders should:

• Set up a security perimeter (e.g., using barrier tape).
• Control access into the scene through the security perimeter.
• Initiate documentation of the scene.

COORDINATE INTERAGENCY ACTIVITIES

First responders must coordinate emergency operations between many different agencies and organizations.

To coordinate activities at the scene, first responders should:

• Establish a command post and implement an incident command system (i.e., a point of contact and line of communication and authority for public safety personnel).
• Establish staging areas to ensure that emergency and support vehicles have access to the area.
• Request additional personnel resources, such as firefighters, EMS personnel, law enforcement officers, investigators, and representatives of utility companies.
• Inform authorities about the status of the incident, hazards, injuries, witnesses, the location of evidence, and other pertinent facts.

EVALUATING THE SCENE

Note:?This section of the guide is intended for the individual responsible for the investigation of a fire incident. At the time the scene is determined to involve an arson or other crime, the investigator must address legal requirements for scene access, search and evidence seizure.

Once a lead investigator arrives at the scene to relieve the?first responders, he or she should evaluate the scene, identify witnesses and survey what must be done. The lead investigator must:

• Contact first responders and establish a presence.
• Define the scene's boundaries.
• Identify and interview witnesses at the scene.
• Assess scene security at the time of the fire.
• Identify the resources required to process the scene.

CONTACT FIRST RESPONDERS AND ESTABLISH A PRESENCE

The investigator should meet with the incident commander and first responders to assess previous events and the current status of the fire scene, make introductions, identify essential personnel, and determine scene safety and integrity issues.

The investigator should:

• Identify and contact the current incident commander and present identification.
• Conduct a briefing with the incident commander to determine who has jurisdiction and authorization (legal right of entry) and to identify other personnel at the scene (e.g., law enforcement, firefighting, emergency medical services, hazardous materials personnel, and utility services personnel).
• Determine the level of assistance required and whether additional personnel is needed.
• Determine initial scene safety prior to entry through observations and discussions with first responders. Consider environmental as well as personnel safety concerns. Assess changes in safety conditions resulting from suppression efforts.

?DEFINE THE SCENE'S BOUNDARIES

The investigator should perform a preliminary scene assessment, determine the area in which the site examination will be conducted and establish the scene perimeter.

The investigator should:

• Make a preliminary scene assessment (an overall tour of the fire scene to determine the extent of the damage, proceeding from areas of least damage to areas of greater damage) to identify areas that warrant further examination, being careful not to disturb evidence.
• Inspect and protect adjacent areas that may include non-fire evidence (e.g., bodies, bloodstains,?latent prints,?or tool marks) or additional fire-related evidence (e.g., unsuccessful ignition sources, fuel containers, and ignitable liquids).
• Mark or re-evaluate the perimeter and establish the procedures for controlling access to the scene.

IDENTIFY AND INTERVIEW WITNESS(ES) AT THE SCENE

The investigator should determine the identities of witnesses and conduct interviews.

The investigator should:

• Contact the incident commander, identify first responders and first-in fire-fighters, and arrange to document their observations either in writing or through recorded interviews.
• Determine who reported the fire. Secure a tape or transcript of the report is available.
• Identify the owner of the building/scene, any occupants, and the person responsible for property management.
• Identify who was last to leave the building/scene and what occurred immediately before they left.
• Identify and interview other witnesses (e.g., neighbors and bystanders) and record their statements.

ASSESS SCENE SECURITY AT THE TIME OF THE FIRE

The investigator should determine whether the building or vehicle was intact and secure and if intrusion alarms or fire detection and suppression systems were operational at the time of the fire.

?The investigator should:

• Ask first responders where an entry was made, what steps were taken to gain entry to the building or vehicle, and whether any systems had been activated when they arrived at the scene.
• Observe and document the condition of doors, windows, other openings, and fire separations (e.g., fire doors). Attempt to determine whether they were open, closed, or compromised at the time of the fire.
• Observe and document the position of timers, switches, valves, and control units for utilities, detection systems, and suppression systems, as well as any alterations to those positions by first responders.
• Contact security and suppression system monitoring agencies to obtain information and available documentation about the design and function of the systems.

IDENTIFY THE RESOURCES REQUIRED TO PROCESS THE SCENE?

The investigator should determine what personnel may be required to process the scene according to National Fire Protection Association (NFPA) 921 and other recognized national guidelines.

Note: Except in the most obvious cases, the determination of a fire's origin and the cause may be a complex and difficult undertaking that requires specialized training and experience as well as knowledge of generally accepted scientific methods of fire investigation.?The investigator must either have the appropriate expertise or call upon the assistance of someone with that knowledge.

The investigator should:

• Identify a distinct origin (the location where the fire started) and an obvious fire cause (ignition source, first fuel ignited, and circumstances of the event that brought the two together).
• If neither the origin nor the cause is immediately obvious, or if there is clear evidence of an incendiary cause, the investigator should
• Conduct a scene examination in accordance with NFPA 921 and other guidelines.
• Seek someone with the expertise required.
• Know when to request the assistance of specialized personnel and to obtain specialized equipment as required to assist with the investigation. Standard equipment should include the following:
• Barrier tape.
• Clean, unused evidence containers (e.g., cans, glass jars, nylon, or polyester bags).
• Compass.
• Decontamination equipment (e.g., buckets, pans, and detergent).
• Evidence tags, labels, and tape.
• Gloves (disposable gloves and work gloves).
• Handtools (e.g., hammers, screwdrivers, knives, and crowbars).
• Lights (e.g., flashlights, spotlights).
• Marker cones or flags.
• Personal protective equipment.
• Photographic equipment.
• Rakes, brooms, spades, etc.
• Tape measures.
• Writing equipment (e.g., notebooks, pens, pencils, and permanent markers).

Note:?If the scene involves arson or other crimes, the investigator must address legal requirements for scene access, search and evidence seizure.

• Recognize the interests of parties that may be affected by the outcome of the investigation and avoid jeopardizing those interests by taking steps to protect evidence. These issues include spoliation, subrogation,?and third-party claims.

DOCUMENTING THE SCENE

After the lead investigator has evaluated the scene, he or she must document the scene. He or she should follow these steps:

Note:?This section of the guide is intended for the individual responsible for the investigation of a fire incident. At the time the scene is determined to involve an arson or other crime, the investigator must address legal requirements for scene access, search and evidence seizure.

• Photograph or videotape the scene.
• Describe and document the scene.

PHOTOGRAPH OR VIDEOTAPE THE SCENE

?The investigator should create and preserve an accurate visual record of the scene and the evidence prior to disturbing the scene.

The investigator should:

• Photograph and/or videotape the assembled crowd and the fire in progress.
• Remove all nonessential personnel from the background when photographing the scene and evidence.
• Photograph the exterior and interior of the fire scene (consider walls, doors, windows, ceilings, and floors) in a systematic and consistent manner. (Videotaping may serve as an additional record but not as a replacement for still photography.)
• Photograph any points or areas of origin, ignition sources, and first material ignited.
• Photograph any physical reconstruction of the scene.
• Maintain photo and video logs. Record the date, the name of the photographer, and the subject.
• Determine whether additional photographic resources are necessary (e.g., aerial photography, infrared photography, or stereo photography).

DESCRIBE AND DOCUMENT THE SCENE

The investigator should create a permanent, documented record of observations to refresh recollections, support the investigator's opinions and conclusions, and support photographic documentation.

The investigator should:

• Prepare a narrative, written descriptions, and observations, including possible fire causes.
• Sketch an accurate representation of the scene and its dimensions, including significant features such as the ceiling height, fuel packages (e.g., combustible contents of the room), doors, windows, and any areas of origin.
• Prepare a detailed diagram using the scene sketch(es), pre-existing diagrams, drawings, floor plans, or architectural or engineering drawings of the scene. This may be done at a later date.
• Determine whether additional documentation resources are necessary.

PROCESSING EVIDENCE AT THE SCENE

After documenting the scene, the investigator or other evidence collectors must collect, preserve and store evidence from the scene. He or she should follow these steps:

Note:?This section of the guide is intended for the individual responsible for the investigation of a fire incident. At the time the scene is determined to involve an arson or other crime, the investigator must address legal requirements for scene access, search and evidence seizure.

• Identify, collect and preserve evidence.
• Prevent evidence contamination.
• Package and transport evidence.
• Establish and maintain the chain of custody.

IDENTIFY, COLLECT AND PRESERVE EVIDENCE

?The investigator should ensure that evidence collectors identify, document, collect and preserve evidence for laboratory analyses, further investigations, and court proceedings.

Evidence collectors should:

• Take precautions to prevent?contamination.
• Document the location of evidence using written notes, sketches, photographs, photo and video logs, the evidence recovery log, evidence tags, and container labels.
• Collect evidence in any areas where the fire originated (such as the first fuel ignited and ignition source) in cases where the fire is not accidental.
• Place evidence in labeled containers for transportation and preservation. Liquid evidence collected for laboratory identification must be immediately placed in clean, unused, vapor-tight containers (e.g., clean, unused paint cans; glass jars; laboratory-approved nylon or polyester bags) and then sealed.
• Label each container so that it is uniquely identified. Labeling may include the name of the investigator, date and time of collection, case number, sample number, description, and location of recovery.
• Collect and preserve suitable comparison samples but recognize that such samples may be unavailable.
• Package evidence in accordance with their laboratories' policies and procedures.
• Recognize the presence of other physical evidence, such as bloodstains, shoe prints,?latent prints?and?trace evidence, and use proper preservation and collection methods or seek qualified assistance.

PREVENT EVIDENCE CONTAMINATION

The investigator should control access to the fire scene after fire suppression and see that evidence is collected, stored, and transported so that it will not be contaminated.

Evidence collectors should:

• Establish and maintain strict control of access to the scene.
• Recognize that fuel-powered tools and equipment present potential contamination sources and should be avoided. When collectors must use these tools and equipment, the investigator should document their use.
• Wear clean, protective outer garments, including footwear.
• Use clean disposable gloves for collecting items of evidence. (To avoid?cross-contamination, gloves should be changed between collecting unrelated items of evidence or when visibly soiled.)
• Use clean or disposable tools for collecting items of evidence from different locations within a scene.
• Place evidence in clean, unused containers and seal immediately.
• Store and ship fire debris evidence containers of evidence collected from different scenes in separate packages.
• Package liquid samples to prevent leakage and ship them separately from other evidence.
• Store and ship fire debris evidence separately from other evidence.
• Follow specific laboratory requests (e.g., to submit an unused sample container).

Note:?In cases of accidental fire, evidence should not be needlessly disturbed, but the property owner or insurer should be notified to avoid issues of spoliation.

PACKAGE AND TRANSPORT EVIDENCE

The investigator should ensure that packaging, transportation, and storage procedures are followed to prevent any destructive changes in the condition of samples.

The personnel responsible for packaging and transport should:

• Take precautions to prevent contamination.
• Package fragile items carefully.
• Freeze or immediately transport items containing soil to the laboratory.
• Transport all volatile samples to the laboratory in a timely manner.
• Comply with shipping regulations.

ESTABLISH AND MAINTAIN THE?CHAIN OF CUSTODY

The investigator should ensure that the chain of custody is maintained.

Personnel responsible for the chain of custody should:

• Maintain written records documenting the sample number, description of the evidence, date, and location where it was found, collector's name, and miscellaneous comments.
• Document all transfers of custody, including the name of the recipient and the date and manner of transfer.
• Document the final disposition of the evidence.

COMPLETING THE INVESTIGATION

Once the evidence has been collected and processed, the investigator must complete the investigation and release the scene. He or she should follow these steps:

Note:?This section of the guide is intended for the individual responsible for the investigation of a fire incident. At the time the scene is determined to involve an arson or other crime, the investigator must address legal requirements for scene access, search and evidence seizure.

• Release the scene.
• Submit reports to the appropriate databases.

RELEASE THE SCENE

The investigator should release the scene after reasonable efforts have been made to identify, collect and remove all evidence from the scene for examination and that all physical characteristics of the scene have been documented. In addition, prior to releasing the scene, associated legal, health, and safety issues must be articulated to the party taking over the investigation and reported to public safety agencies if necessary.

The investigator should ensure that the following tasks are completed before releasing the scene:

• Perform a final critical review:
• Ensure that all evidence is inventoried and in custody.
• Discuss preliminary scene findings with?team members.
• Discuss post-scene issues including forensic testing, insurance inquiries, interview results, and criminal histories.
• Assign post-scene responsibilities to law enforcement personnel and other investigators.
• Address legal considerations.
• Verify that all scene documentation has been completed.
• Address structural, environmental, health, and safety issues.
• Remove all investigative equipment and materials.
• Recover and inventory equipment.
• Decontaminate equipment and personnel.
• Document the following information:
• Time and date of release.
• Receiving party.
• Authority releasing the scene.
• Condition of the scene at the time of release (e.g., structural, environmental, health and safety issues). Consider photographing and/or videotaping the final condition of the scene.
• Cautions are given to the receiving party upon release (e.g., safety concerns, conditions, evidence, legal issues).

SUBMIT REPORTS TO THE APPROPRIATE DATABASES

The responsible agencies must file incident reports with the appropriate databases. Detailed fire information is collected, integrated, and disseminated through national and state databases. These data help authorities identify fire trends and develop innovative procedures and equipment.

The investigator should collect sufficient information and report it to the following databases:

• Arson and Explosives National Repository.
• Bomb Data Center.
• National Fire Incident Reporting System.
• National Incident-Based Reporting System.
• State and local fire incident reporting systems.