Arson Investigation Physical and Chemical Evidence 4380 2020

Today's video from Kimber is about

arson

evidence

, so this is an interesting field that has changed quite a bit over the last few decades, probably the last 30 years, so today we're going to cover some interesting topics so that whenever you there is an

arson

or some type of explosion it is quite difficult to find the

evidence

sometimes the circumstances are difficult what is also interesting is that a friend of mine who is an arson investigator said that he calls the fire department the destruction department evidence because every time there is a fire one of the The questions, as always, were this accidental or intentional, so they must come and identify the relevant

chemical

materials.

If there was an explosion, they have to see if it was like a boiling liquid explosion or if it was detonated with some device so they could be looking for lighters or timing devices and then they have to try to reconstruct the event, so this is a little difficult because Much of the evidence is destroyed, but not always not all of the evidence, as we saw in the last video about explosives, how They were able to find fragments of the circuit board used to bring down Pan Am Flight 103 and that was an explosion that occurred in the air and the plane was destroyed and about 10,000 pieces and they still found the luggage that the bomb was in and They found a circuit board from the cassette player that indicated that the bomb was inside and the timing device, so for the fire

investigation

it is really difficult, as I said the evidence is destroyed so you need to identify where the fire started and if it started on the first floor, it started in the attic, was it electrical etc when I say it was intentional, if it was the first floor, the heat increases, so it will be very easy to find out that it started on the first floor, maybe you will know if it was fire. is completely involved in the building and started in the flowers, the evidence may be totally destroyed as to what started the fire.

Let's look at a house fire here, and this is a good example of what we call a V pattern for fire. You can see this obviously started here in this red circle. It looks kind of like a V from heat damage caused by fire, but these are some polyester or cotton curtains. There was a fire in this room and these curtains are not altered. There may have been some smoke damage, but no heat reached here. The heat obviously started here due to carbonization and you can see some kind of V pattern. These curtains were melted or cooked somehow and then on the ceiling you see some smoke.

The damage occurred here, so it's a huge B pattern and that V will point to the origin of the fire in many cases, so let's zoom in on this little red square. It was intentional, you know, there was gasoline spilled in the corner of the room and then they closed the door and left and maybe you lit it so it went under the door, that's a possibility, but let's see what we find if we go to this corner , behind that door you see a lot of debris that came off the wall, so maybe some wallpaper that burned and fell off, but maybe there's a little more debris, maybe there's charred magazines and things like that and then this looks like a burned out outlet so maybe that outlet got hot enough to set these papers on fire there's some that look like some wet debris here maybe there's some relevant evidence of arson there so if you were to walk into this as an investigator, you would want to pick up some evidence, take it to the bottom of this ash pile to try to find if an accelerant was used and then you could have a fire can and the evidence can and you'll see some of them on a later slide and you would use tweezers and gloves and you would collect the evidence, put it in this airtight can and hammer the top like it was a pain.

You could hammer the top chef and fill in the location where you collected the evidence, etc., and then you would take him back to the lab to see him, but this was definitely the source or origin of the fire in this structure, so we could look at the fire scene , you start examining a fire as soon as the fire department lets you go in there; In fact, many of the arson investigators are firefighters, so as soon as they think the room is stable enough to enter without you know the hoses blaring, then you can go in and begin your

investigation

.

Experience shows that most arson fires are started with petroleum-based accelerants, so that will be the most common indicator that an arson fire is something that is combustible or flammable. Now the difference between combustible and flammable is the flash point, so if it has a flash point less than 100 degrees Fahrenheit, then we call that substance flammable, but if it's not flammable, that doesn't mean it won't burn as if Diesel is classified as a fuel because its flash point is above 100 degrees Fahrenheit. All the flash point means is that the flame, if you have a puddle of fuel and you have a flame nearby, it will spontaneously jump from the flame to the puddle of fuel and it will burn on top of the fuel, it will flash on top. of the fuel and you have to raise the temperature of that fuel above its flash point for this phenomenon to occur, so 100 Fahrenheit is just an administrative number that we set, so if it flashes at temperatures below 100 Fahrenheit, then We call it flammable and if it's above 100 degrees Fahrenheit I call it combustible, so you may find petroleum based accelerants soaked into a carpet or paper or maybe a wallpaper if it was splashed on the wall, so I would look for those oil-based firms. in your subsequent forensic analysis, then there is such a need because these petroleum based accelerants are volatile and you have been in a hot environment, the chances of them evaporating and the evidence being lost or high, this is an example where The investigation takes priority, so if there has been a fire, the fire department has responded.

The door is now open for the arson investigator to enter and investigate the fire. They can begin that investigation immediately and don't have to wait for a search warrant. The search for the fire scene should focus on finding the source and that is where we will find the most likely evidence of an accelerant if it was arson or some type of ignition of a device there are some telltale signs of arson such as If they have streamers on the floor, sometimes or oil-soaked rags can connect the fire from one room to another or even ropes or, more commonly, simply pouring gasoline along the floor where the fire will spread through that gasoline coil, this is a telltale sign, then The fire will have multiple origins, you will have V-shaped charring in several rooms or you will see burn patterns on the floor and normally the fire has a tendency to move upwards, so we can find that V pattern . and look at the bottom of the V for the source of the fire, the origin of the fire and interestingly, combustible liquids are rarely completely consumed during a fire so some residue is almost always left behind and this is the real key. for the investigation of arson. is a NIJ report that is available on the Blackboard site and this is quite interesting.

They have a fire testing lab that has a warehouse, it has a kind of concrete platform that they can put floors and other types of things on and then they have a giant hood. which is on top of that that draws all the smoke and everything through some scrubbers and so if they can work in that warehouse while the fires are happening and not be exposed to smoke or something like that, they can put thermal imaging there and measure the heat that comes from different materials, they can measure the heat from the smoke, they can look at these combustion patterns, so this is a really interesting report to read.

They won't evaluate it in this entire report, it has many pages, but but. There are some interesting findings for arson research. One thing we will look at is burn patterns on the floor, so here is a photo of the floor they laid. This is in your warehouse. There is a ventilation hood above this, so all the heat is smoke. They are going up on the hood so they can set up their equipment and work here while the fire continues and not be in danger. What they wanted to do in this report is to see if they put a gallon of gasoline in the fuel, what size ring would it make and then they would set it on fire and They would see if the combustion pattern matched the size of the liquid ring and if that could be linked to the volume of gasoline they poured in now, most likely a carpet, that will be the case, but what about the tile floor? ?

Here it's like a linoleum tile floor, here it's a parquet floor, a wood floor, so they poured gasoline on these different types of floors, started them up, measured the carbonization, and looked to see if there was accelerator residue on them. the floor and it's Like I said, it's a fantastic report, so here are some takeaways from this report: The area of ​​the spill can be predicted by the amount of fuel, so if you look at the size of the spill area, it will obviously be larger if you have a larger report. A large amount of fuel was poured onto that surface, so the burned areas of the carpet were found to be the same as the spill areas of the carpet.

Note that the burn and the spill are two different things, so the spill area was maybe about two feet wide and then the burned area was also two feet wide. wide, so this matched in terms of carpet, so when you look at the burned area on the carpet, you can assume that's how big the spill area was, so if it's a small spill area, then it may be accidental if it is a huge spill area. then there is probably someone trying to set the fire, so you would also have to evaluate the totality of the circumstances to see if there were other indicators of insurance flora fraud, so let's say they just take out all your furniture before continuing. vacation, whoever does that would have to explain why they took their furniture out of the house and while there was gasoline on the carpet and it ignited right when they went on vacation, again, it's not just the presence of an accelerant that turns it into a fire provoked but under the totality of the circumstances in the investigation, the amount of gasoline could be determined from the burning pattern on non-porous floors, and significant amounts of the spill tool were present after the extinction of the carpet fires, for what this melted mat inside the donut protected the unburned. liquid and then this donut, if you're talking, it's this donut burning pattern, so if you have a puddle of fuel right here on the carpet, it's not the liquid that burns amazingly, I mean, just think about your candle, you light a candle and it's the flame from the wick that melts the candle and then that liquid wax doesn't burn well and if it did the flame would go down on the liquid wax and it would just burst into flames which would be a dangerous Kendall.

It is the steam that burns. Well wax just isn't volatile so there isn't much vapor wax on top of the liquid vapor where the liquid wax flows up the wick and then the heat causes the wax molecules to break down so there are clumps propyl, butyl groups and ethyl groups that are cleaved. These long, 20-carbon wax molecules are so small that it's those smaller compounds that are the breakdown products that actually burn into the wax. Well, something similar happens with gasoline: you pour gasoline on the carpet and it is the vapor on the liquid that burns and the liquid will heat up. but it will not exceed its boiling point because that is how things are.

I mean, when you boil a liquid there is a temperature pause at the boiling point and that temperature will remain there until all the liquids evaporate and that boiling point of the gasoline or diesel will protect the carpet it is soaked in, for which, when dry, will set fire to the carpet so that they burn. The carpet around the outside and then in the middle, where there is still liquid fuel, will have liquid fuel and maybe some melted carpet fibers, but as long as there is liquid fuel in the middle, it will never exceed the boiling point of that liquid, so that you will retain some of the liquid accelerant in the center of this donut burning pattern, you put out this fire.

There will be a black donut and maybe even an unburned, maybe even unmelted, rug right in the middle, we don't really see much of a donut pattern on the non-porous floor, so you see the flames follow the grooves in the wood. look here, but that just means there's liquid underneath in those cracks, so you might be able to pop some of these pieces of wood and on the back you'll have some of theflame, some of the liquid accelerant, so if I was coming to investigate this particular fire. I would prepare my arsonist relatives. Now we have a screwdriver or a knife.

It would appear in the corners of some of these slabs, break the wood and stick it into the fire can and seal it. immediately and then maybe even put it in a freezer so the maximum heat release rates on non-porous surfaces were examined and these were about 1/4 to 1/8 of the heat release rates of a fire in a pool so they can calibrate it with the pool, so if you have diesel and you put it like a pan, okay, so you have a pool of diesel in a pan and you heat it so that it ignites and then you set it on fire and so that diesel is is burning in a diesel pool and you measured the amount of heat coming out of that, that's what's called a pool fire and it says I'm the non-porous floor like the tile floor, the heat coming out of that fire was only about 1/4 to 1/8 of the heat released from a pool of diesel because the diesel has soaked into the cracks in the floor and can't burn as fast and is simply sinking the heat over the larger area, except in the case of the carpets. the heat release was approximately equal to that of a pool fire, so a diesel or gasoline poured on a carpet is like burning pure gasoline now evidence collection must be collected as quickly as possible and then placed in an airtight container many times There is a small septum at the top a small silicone rubber gasket so you can stick a needle in and take samples of the hair hairs that are in the air space above the evidence, so traces of this liquid residue can be locate with a vapor sniffer or a dog, so you can have arson dogs that smell gasoline and can find the accelerant if it is difficult to find the point of origin.

I can also use vapor detectors or gas detectors so it's also important to sample similar but uncontaminated control samples so if I were to use that for floors like I said I would pick up the wood floor where it was burned I would pick some of those pieces. Remove them into an arson can and seal it. I would also go to a spot on the floor that hasn't burned. This is really important. I would take some of those pieces off and put them in an arson can too, because what if that's the case? The signature I called diesel fuel was actually just a treatment on the entire wood floor and you could suspect an accelerant when it actually wasn't and you could be putting an innocent person in danger of going to jail, also a search for a lighter. like matches or some type of spark generating device or maybe even parts of a Molotov cocktail, so maybe you've never heard of a Molotov cocktail.

You see this in some of the riots that you can see on television and it's gasoline or some type of flammable liquid placed in a breakable jar like a glass bottle and then you like this match, then the match burns and then you throw it and when the glass breaks, the flammable liquid is released and it goes from just a match flame to a huge burst of flames and that's called a Molotov cocktail. I'm not exactly sure where that name came from. Here are the evidence cans and I think these are the best because they are metal.

Now that you know, in face-to-face class, I would ask you. to tell me why you think it's metal is important, but since we don't have the ability to interact here, metal is important because it's impermeable to gas, so you're not going to let the vapors escape through the walls of the container and So here's the septum I was talking about, it's a silicone rubber septum and there's a step so you can insert a needle through the top of this septum and sample the headspace inside this incendiary can. Sometimes they heat the incendiary canister and make the accelerator more volatile and they will take the gas out of this canister and put it into a gas chromatograph.

There are also nylon evidence bags, but I don't like them because nylon potentially lets vapors through, so it could let some of that gasoline evidence or something volatile escape through the bag. I think it's much more defensible to use a metal can instead of a polymer bag, so let's look at some of the different types of analysis techniques. Remember we're Actually, let's imagine we're trying to collect gasoline, so how do we get gasoline from a floor surface like a carpet and get it into our gas chromatograph so we can analyze it? Well, here's a way to do it.

Take the evidence out of the evidence container, place it on a small heat source and then we can have a small cover that removes that material and we call it a kind of trap, so this this source of vapor is pushing vapor. which is again that the heat source and pushes it into a trap, a trap could be some type of absorbent material, so this is steam distillation, so using clean steam to vaporize the volatile compound components of our evidence and putting them in an absorbent trap could be like molecular sieves or something like that and then you would extract the evidence from the gasoline if you were from the trap material into something that is very, very volatile like a pentane, you would say well what if they used pentane as an accelerator?

Pentane will boil in your hand, it's so volatile that it won't be useful as a liquid accelerator, so you could desorb that trap into pentane distally and then you could run it in a gas chromatograph. Another way is to use solvent. extraction, so instead of using heat to push it into the trap, maybe you could just wash the evidence with a solvent like pentane or carbon disulfide, so carbon disulfide is a good solvent, although it is quite toxic, but it won't be very useful as an accelerator either. so it's not going to interfere with gasoline, hexane or diesel fuel, etc., so you can put the solvent in the waste container, wash it, extract it or pour it into an evaporation dish, evaporate it, which makes it It will concentrate and then you can take it to the gas chromatograph, so this would be a great extraction method.

Now these numbers are ASTM numbers and these would be the ASTM for these different techniques. You could just heat the container and use that partition, put a gas syringe in there and take a sample of the gas. it would be headspace sampling, so you can go right from the syringe and inject like a milliliter of headspace gas directly into the eye of the gas chromatograph. You can use passive headspace absorption, so you could place a carbon strip. Now coal has a huge surface area and is very attractive. to the organic molecules, so first you have to activate it to heat this charcoal to remove all the volatile organic compounds and then you can place this strip of charcoal in the headspace and any of the volatile compounds will come off the evidence and land. on the carbon strip and it gets stuck, then you can extract it with an extraction solvent like pentane and place it under the GC.

You can use a purge gas such as helium, neon, purge gas. We call this purging and trapping so that it purges it through the container and then you have an absorbent like carbon and then you have gas chromatographs that can put these absorbances directly into the Aleut stream or you can extract the compounds from that absorbent. using carbon disulfide and then putting it in the GC and then more recently this technique has really been phased out, it's called solid phase microextraction and they have these silicon polymers like phenylsiloxane and you can have this little needle or a fiber and it's inside a little protective sleeve, so you have a metal sleeve that's strong, it can go through that septum, so you'll bleed it or pierce it through that septum and then you push down this little plunger and out comes this needle that has a clean polymer and the molecules that are in the headspace will stick together. that polymer and now these some siloxane polymers are very strong and very stable at high temperatures, so they can withstand the two hundred and eighty degree inlet temperature of a GC, but the other volatile compounds will come off, so the volatile compounds They adhere to the fiber.

You pull the plunger up so the fiber goes back into the metal sleeve, you pull it out and insert it into the GC injector and you push the little fiber down and now the fiber is at a two hundred and eighty degree entrance and the compounds volatiles come out of the fiber and then go through the gas chromatograph, the SPM, a solid phase microextraction is a great technique, it is not very quantitative but qualitative, so you will get a particular set of peaks that have a pattern related to the diesel or gasoline or some other type. of combustible fluid, so let's look at some of the data we obtain from these in the laboratory, the gas chromatograph is the most sensitive and reliable instrument to detect these flammable wastes and, since the majority of these arson fires are started by by-products of the oil from these traces of GC the SEP, the different retention times and their relative compounds will be like a fingerprint for the different materials, so let's look at some of the liquids that have been analyzed in GC, so it also depends on the technique, as you can imagine. would be solid phase microextraction of the headspace and you would see this pattern, say of a particular fuel, and then the static headspace will have a slightly different pattern because a slightly different extraction mechanism extracted the different compounds at different concentrations, so the take home lesson here is If you have a database that was developed using dynamic headspace and you can't use it reliably, then solid phase microextraction will give you a perfect match.

Now it will still show you several of the same peaks, but notice how they all have slightly different relative values. intensities, so this just means that if you're going to use solid phase microextraction for arson research, you really need to set up a sample library and run multiple analyzes of the samples, so diesel might be taken two or three times and put in your library you use SPME and then gasoline and then you might even want to use regular and high octane gasoline because they may have slightly different chromatographs so let's look at different types of things that we'll look at in the house to not use only accelerators. but do things that can also be found around the house, like shoe polish or wd-40, furniture polish, mineral spirits or maybe insecticides, and here are a bunch of different household items and these are the different chromatograms so you can see the different carbons.

The chains that come off from this look like 10a Cielo and ac-12 and then various fragments due to different functional groups. You can see wd-40 is mostly c10 so you know 10 carbons and then this could be a little bit oxidized c10 that's what it has. a little bit heavier mass, maybe there are some oxygens that have attacked that main chain, you have some c9 and c11, the propellant and the r8 insecticide or the solvent that contains the active ingredient is a little bit heavier, you know that its component main is c-13, but it is You have a wide variety of different carbon peaks, so most of these are hydrocarbons.

You have some functional groups in between, so you have to have controls. These evidence images are also essential. You need to see the V pattern you need to see. you know, document the whole scene and the thing is, it would be a travesty to arrest a good housewife for arson, so if you saw that it looked like the fire started on a piece of one in the corner of the room and you didn't take samples of that wood and saw that you thought it was diesel fuel, but maybe the good housewife used furniture polish with lemon oil.

These are very similar chromatograms, so you would want to find a sample of that that will object that it hasn't been burned or scraped. some of it he put in the fire can because that would give it the lemon oil furniture polish signature and the burned area may still have some lemon oil furniture polish on it and it could be mistakenly said to be combustible diesel, so that's what I mean by controls: you need to sample some unburned areas and some burned areas and then your database in the lab should have as many household objects as possible so you can rule out diesel or gasoline if of In fact, it's wd-40, so arson investigation is one of the most challenging areas in forensic science in the past, like over 20 or 30 years ago, the conventional wisdom was that if you saw cracked glass like this , where you could see spalling concrete, that was evidence of extremely high heat and that's why they would label this arson because they thought that only by using an accelerant that would produce extreme heat conditions would you get these types of signatures.

Also melted metal they said it wouldn't melt metal andThat's not true, my son and I. Make this in our backyard with leaves and candy gumballs, we melt aluminum cans and pour them into muffin tins to make aluminum ingots and it's the heating rate, not the burning, so you can have bed springs flattened, like the ones that used to be listed as evidence of arson and then burned at floor level, so it starts with a V flame pattern, but eventually the entire floor can burn and they would say that was evidence of arson because the floor didn't show a V. pattern that the entire floor burned but they have a condition called flashover so first you get a feeding pattern then the roof catches and then when the roof starts to break down you have gas burning at the top of the room and that's called flashover, so you just have this gas burning from decay products in the room that's at the top of the room because the heat increases, but then the radiative heating of that fuel burning at the top of the room will set the floor on fire, so radiative heating is what it is. sets the floor on fire, not convection heating, convection heating is molecules colliding with each other and that's what causes the heat to rise and that's why the convection oven has a Azzam has a fan in there, it's pushing currents of air so convection heating burns the ceiling but radiation heating burns the floor and so initially you will see it in the burn pattern but then once it comes on you have radiative heating in Many of these conclusions were overturned with some of the California fires when entire neighborhoods burned.

The ground because of some of these wildfires in California, arson investigators were able to get in there, they knew people had been evacuated from their homes and therefore no one was there to start the fire, this was just a natural external cause and entered. and they saw cracked glass, they saw chipped concrete, they saw melted metal, box springs crushed at floor level, burning and so it overturned a lot of this conventional wisdom, but it was sad because in the past many people would be convicted of arson because of these phenomena that they occur naturally. They were classified as arson by conventional wisdom, so in the last 20 years, about 20 years, many of these indicators have been observed in unarsoned home fires and we have more accurate data.

Research like this is a snapshot of some of the the thermal cameras and so on used in Nist's fire investigation facilities, so I hope you enjoyed this video about arson investigation. It's another area you can delve into with your forensic chemistry degree and I think you know it. It would be an excellent use of your skills.