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Arson Science Rewritten 152

Posted by Zonk
from the tis-the-season-burn-burn-burn dept.
An anonymous reader handed us a link to an AP story about advances in the science of arson investigation. Many assumptions about fire, long held by investigators, have been overturned in recent years as scientists have come to understand concepts like 'flashover'. The repercussions of these findings is having an effect not unlike the use of DNA in crime-solving; people are being set free, and old cases are being re-examined. From the article: "Significantly, flashover can create very hot and very fast-moving fires. And it can occur within just a few minutes, dashing the concept that only arson fires fueled by accelerants can quickly rage out of control. The studies began to chip away at the old beliefs -- critics call them myths -- but it took years. Through the 1980s, texts at the National Fire Academy in Emmitsburg, Md., still taught the traditional techniques. It wasn't until 1992, when a guide to fire investigations by the National Fire Protection Association -- 'NFPA921: Guide for Fire and Explosion Investigations' -- clearly laid out, in a document relied upon by authorities nationwide, that the earlier beliefs were wrong."
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Arson Science Rewritten

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  • by Anonymous Coward on Sunday December 10, 2006 @12:31AM (#17181722)
    you would be skeptical about the need for "accelerants". If you've ever seen a fire move through a room, it can go from a small area to engulfing the entire thing in less than a minute without any help from gasoline etc. I'm pretty sure that what happens is that the heat from the small fire vaporizes ordinary non-volatile things, like household furnishings or materials, and those vapors then act as the accelerant.

    I know there was a case a few years ago where an "arsonist" in TX was executed for having killed his family, and within less than a year it was established that he was innocent.

    I'll just say, the idea of someone being executed based on expert testimony from arson investigators, who are not even scientists, is appalling. Experts are only right until some new piece of knowledge comes along and changes the field.
    • by Swimport (1034164) on Sunday December 10, 2006 @12:38AM (#17181778) Homepage
      I know there was a case a few years ago where an "arsonist" in TX was executed for having killed his family, and within less than a year it was established that he was innocent.

      What? An innocent man was executed in Texas? I highly doubt that.
    • by Somatic (888514) on Sunday December 10, 2006 @01:38AM (#17182112) Journal
      that this thread will turn into a flame war.
    • by failure-man (870605) <failureman@gmail . c om> on Sunday December 10, 2006 @02:25AM (#17182330)
      This is why the entire civilized world (rest of?) has done away with the death penalty. If (and when) the criminal justice system fucks up you can't just go "Oops, sorry dude. Ctrl-Z on killing you." Imprisoning them for years by mistake is terrible, but at least you can let them out.
      • by TheLink (130905)
        That said, might not be such a great thing to just let someone out after many decades when they are 70+ years old with near zero savings in a country with not much welfare, without helping to take care of them.

        Even if they have relatives.
      • by Kokuyo (549451)
        I do believe that a civilized country does not have a death penalty. That said, I also believe that not every country that has no death penalty is civilized either.
    • Experts are only right until some new piece of knowledge comes along and changes the field.
      Yeah, it's called the scientific method [wikipedia.org]. It's a bitch, ain't it?

      What you didn't mention is that new evidence can come along and solidify a field. Just because the scientific method can disprove preconceived theories doesn't negate the power of science, which is what I read that you are implying. At least toward evidence for a death penalty, but if you believe that you cannot rely on science then what can you rely upon?
      • by Anonymous Coward on Sunday December 10, 2006 @04:12AM (#17182792)
        Just because the scientific method can disprove preconceived theories doesn't negate the power of science, which is what I read that you are implying. At least toward evidence for a death penalty, but if you believe that you cannot rely on science then what can you rely upon?

        What it appears he's saying is that, given that long-held scientific beliefs can and are overturned but killing someone cannot be overturned, perhaps scientific evidence isn't enough to justify killing someone who isn't presenting an immediate threat.
      • Re: (Score:3, Insightful)

        by norton_I (64015)
        The article made it clear that the "old" rules about fire progression were not based on scientific study. Simple observation is the beginning of scientific investigation, but it is not itself scientific investigation.
        • Re: (Score:3, Insightful)

          by timeOday (582209)
          The problem is separating fact from conventional wisdom. Almost all of what we as individuals "know" is what we've heard from other people. There just isn't time for every person to reproduce all of human knowlege from first principles. Raise your hand if you believe e=mc^2. Now raise your hand if you can derive it from first principles (or even list the "first principles" in question). People do not (and perhaps cannot) track all the uncertainty of their knowledge, and their conclusions from that know
      • by rohan972 (880586)
        but if you believe that you cannot rely on science then what can you rely upon?

        Speaking strictly of evidence for court cases: eyewitness testimony, together with a requirement that if someone is found to have lied, they get the same penalty the accused would have if found guilty.
    • by dbIII (701233)

      I'll just say, the idea of someone being executed based on expert testimony from arson investigators, who are not even scientists,

      It's the Tom Clancy fantasy of the competant but uneducated expert who has picked everything up by osmosis without making any mistakes and never listens to anyone else - people think this sort of thing is real. I'm willing to bet the arson investigators in the US are not that bad and send things off for lab testing to get results from people that are experts in each thing or ge

    • by teflaime (738532)
      I'll just say, the idea of someone being executed based on expert testimony from arson investigators, who are not even scientists, is appalling. Experts are only right until some new piece of knowledge comes along and changes the field.

      You are grossly misinformed. Most professional arson investigators are fire fighters who have been extensively trained in fire sciences. In fact, to be accorded official status as an arson investigator in many states, you must complete an extensive training course in fire
      • Where we once didn't have materials that could flash over in common use in the household...

        Uh, talcum powder, wheat flour, any loose weave cloth used as wall hangings or bed linens, *sheet rock* (yup, get it hot enough, and it'll go up quite fwooshedly), Xmas trees, saw dust, in fact, anything that'll burn, if reduced to dust in the air, will flash over.
        • by Ihlosi (895663)
          if reduced to dust in the air,

          Not just dust. If it gives of flammable vapors when heated (*WOOD*. Basically, _any_ organic molecule will break down into smaller, more flammable molecules when heated), it can cause flashover.
  • by Catbeller (118204) on Sunday December 10, 2006 @12:42AM (#17181796) Homepage
    And Jay Leno made jokes about me getting set on fire in prison. And all the inmates were so aglow with inner certainty as I was gang raped to death. Gosh, I guess no harm, no foul.

    -signed, dead guy who was obviously guilty
  • by dsci (658278) on Sunday December 10, 2006 @12:45AM (#17181818) Homepage
    I used to be a volunteer firefighter and also served as a fire investigator. My experience began around 1981 or so; later (late 90s), I worked for a Police Department doing crime scene work and part of that was fire investigation.

    From TFA:

    Up until the 1990s, this is what fire investigators were taught:

    Fires always burn up, not down.


    I was NEVER taught that; just the opposite. Fires tend to burn up FASTER than they burn down, but geez, anyone who has ever actually WATCHED a fire burn knows this statement is nonsense.

    Fires that burn very fast are fueled by accelerants; "normal" fires burn slowly.

    I was NEVER taught that; just the opposite. We were taught that accelerates were ONE WAY a fire MIGHT burn faster than you would expect under similar conditions. We were also taught that is EXTREMELY difficult to gauge how fast a fire "should have" burned. I did my first chemical test on fire debris in 1986 using GC/MS via a very simple headspace analysis on a sample that the state lab sent back as negative (my test was positive for something, perhaps ambient artifacts, but was an educational run, not an 'official' test). With the negative test result, we sure did not try to use evidence of 'how fast that fired burned' to assert the presence of an accelerant.

    Arsons fueled by accelerants burn hotter than "normal" fires.

    Somebody is oversimplifying the concept of "fire load" here. There are a WHOLE LOT of things than can make a fire burn hotter than 'normal.' In fact, as a common theme I am trying to represent, "normal" is not a well defined term for real-world fires. Rural firefighters and investigators certainly knew this before 1992.

    In fact, this statement glosses over another issue about arson - they often, quite often, don't involve 'accelerants' at all.

    The clues to arson are clear. Burn holes on the floor indicate multiple points of origin. Finely cracked glass (called "crazed glass") proves a hotter-than-normal fire. So does the collapse of the springs in bedding or furniture, and the appearance of large blisters on charred wood, known as "alligatoring."

    The clues to arson are clear?? Man, I clearly remember in the early 1980's being taught exactly the OPPOSITE of what this article says was the "norm" back then. Perhaps it was taught somewhere, but not in RURAL North Carolina. Absolutely NONE of these "clues" are evidence of arson - only of certain fire conditions.

    What we were taught in our arson investigation classes, and what I came to learn through experience, is that arson was/is and EXTREMELY difficult crime to prove. That means it is difficult to prove that a fire was arson, much less who did it.

    Truthfully, based on my experience, I don't see the point of this article. It asserts 'beliefs' about fire investigation pre-1992 that just are not true.

    And finally, the article gives the tragic story of the Lee family that occured in 1989. While presenting NONE of the evidence that was used to convict him, the story creates the straw man that just because it was 1989 and fire investigation changed (around then, according to the article), he must be framed. I don't know of his guilt or innocence, but that's a might big leap of logic.
    • Re: (Score:3, Insightful)

      by shawn(at)fsu (447153)
      Fires always burn up, not down.
      That comment made me think, I've heard it countless times on TV shows etc. Right now I just thought about how many times I've burnt my fingers holding a lit match.
    • by blackdropbear (554444) on Sunday December 10, 2006 @01:31AM (#17182072)
      Its also interesting that flash over may not be confined to restricted sapces like rooms. I have heard of similar effects occuring in the late 1960's in a very hot eucalypt fire. The gases boiling out from the eucalypt fire were trapped by an air inversion until eventualy the whole valley ignited and erupted in a ball of flame.
      • Re: (Score:3, Interesting)

        by willpall (632050)
        I believe you're talking about the Loop Fire [fireleadership.gov]. There are some interesting articles on it at that site [fireleadership.gov] as well.
    • Arson science is so advanced; it can tell the difference between a cigarette inadvertantly thrown in the trash and one purposefully thrown in. I heard they get psychic investigators to do the actual analysis.
      • by Dun Malg (230075)

        Arson science is so advanced; it can tell the difference between a cigarette inadvertantly thrown in the trash and one purposefully thrown in. I heard they get psychic investigators to do the actual analysis.

        You know, it's funny, but if there's one thing I've learned from watch all those true crime shows on A&E over the years, it's that most police investigators don't solve crimes by collecting evidence until they have enough to point to the guilty party. On the contrary, they frequently "have a hunch" or "follow their gut" and then badger the suspects until somebody 'fesses up, or someone with a beef with the perpetrator drops a dime on them. Sure, they have all sorts of ways of justifying their "hunches"

        • Re: (Score:3, Interesting)

          by green1 (322787)
          I have had a hand in evidence collection for a couple of murders now, and what I have learned from the detectives involved is that you don't find evidence that tells you who in the whole world did it. what you do is figure out who the principal suspects are, and then find evidence which proves which one of them did it. eg: finding a cigarette package at the scene of the crime doesn't tell you who did it, but when only one of your suspects smokes, it's a pretty good indicator.

          items and conditions found at th
    • >> Fires always burn up, not down.

      > I was NEVER taught that; just the opposite. Fires tend to burn up FASTER than they burn down, but geez, anyone who has ever actually WATCHED a fire burn knows this statement is nonsense.


      Or anyone who watches TV, since they explained that on CSI a few years ago. Perhaps firemen should watch more TV; I know I get all my useful information from there. (Well, sometimes Wikipedia, especially the fast-changing articles, those are the most reliable.)
    • Bingo. I, too, was a volunteer fire firefighter in the mid 1980's. Flashover (of perfectly natural fires, forest fires, car fires, flame wars) was taught extensively. Anytime you have heat, combustible materials and some oxygen, in a partially enclosed space you can get flashover. Try breaking a window in a smoldering house (without sticking the hose in another one). Poof, flashover.

      Arson was a possibility but not a given. The article was pretty bizarre, I couldn't figure out why they're talking abou

    • Parent here is right on. There are pointers to arson, but the stuff cited in TFA isn't what I was taught. These were some of the indicators of arson:
      • Presence of accelerants - look for pour patterns on the floor.
      • Multiple points of origin - clear indicators that the fire started in two, three or more places.
      • Personal valuables missing - absence of photo albums, personal phone book by phone, pictures missing from wall, stereo, cameras, etc. missing. I once investigated a fire where I found ammo for five
  • Dammit (Score:2, Funny)

    by quokkapox (847798)

    It took 18 years to get that freakin song out of my head.

    Now, I unleash my revenge:


    Einstein, James Dean, Brooklyn's got a winning team
    Davy Crockett, "Peter Pan", Elvis Presley, Disneyland

    Bwahahahahaha...

  • by Anonymous Coward
    Why the heck should all houses in this country be made of wood? Haven't you guys heard of concrete? Or good old bricks? Seriously, this is crazy.
    • Re: (Score:3, Insightful)

      by jbevren (10665)
      Sad thing is, mansonry conducts heat. While some regions might not consider this a problem, try living in a brick house when the temperature drops below 0 farenheight. It can't be fun, so the solution is to build a brick exterior and set up a wooden insulated studwall on the interior.

      Besides, what is going to hold up your concrete second floor? Or is it that all houses in your country have no cellars or second floors? The cost of constructing a house made entirely of mortar, brick, and stone is immense.
      • Re: (Score:1, Informative)

        by Anonymous Coward
        On the Pacific coast, very few buildings are built out of brick or masonry, for three important reasons: 1) it's expensive, 2) along much of the Pacific coast there's an abundant supply of wood, and 3) they tend to fall down for reasons entirely unrelated to fire.

        Irrespective of what your house is made of, one of the keys to keeping it from burning is a non-flammable roof. Many houses succumb to fire when another fire outside the house (forest fire, nearby building fire, brush fire, etc...) drops flaming ma
      • Re:Wooden houses? (Score:5, Insightful)

        by loraksus (171574) on Sunday December 10, 2006 @02:11AM (#17182260) Homepage
        Pretty much all (Western and Eastern) European home construction is concrete / brick based and this extends through most of Russia and large parts of the rest of the world. Building out of wood is a foreign concept for a large number of people in the world. Many countries don't exactly have huge forests either - nothing like what we enjoy in North America.
        Basically Europe is completely deforested. There are forests, sure, but they would be gone pretty quickly if people started building homes out of wood.

        As for the engineering aspects - concrete is strong and you can easily drop a concrete slab as the floor on your second story if you use walls of reasonable thickness - or you can use wood flooring suspended on a central beam(s) or one of dozens of other ways that builders use to suspend a floor in a wood house. Very few houses in Europe are only 1 story.

        I've seen pre-fabed buildings being put together (and quickly) in Poland and Eastern Europe using both methods - a crane, a few hours and a welder is all it takes to get the structure done since the buildings come on the truck with rebar in place, holes and supports already in the concrete. Pretty cool actually.

        Assembling a house out of brick isn't terribly difficult either - many people in Eastern Europe build their own houses, by hand, slowly, after they come back from their day jobs or whatever. Try doing that with wood construction and you'll end up with a crooked house that falls down in a year.

        There is also a newer technology under the category of "insulated concrete forms" (ICF) - basically big hollow styrofoam blocks that you assemble like legos and fill with concrete (they have internal structure and rebar holding them together)

        A house built with ICF has superior insulating properties (and does a fair job of blocking wifi signals too ;)
        • Re: (Score:3, Informative)

          by tetromino (807969)
          IMHO, the difference in building materials can mostly be explained by the differences in the buildings.

          Americans typically live in small, freestanding, single-family houses. For such small buildings, a wood+drywall construction is probably the most cost-efficient, especially considering North America's plentiful supplies of lumber. On the other hand, Europeans tend to live in apartment buildings, which require the use of stronger materials like brick, cinder block, and reinforced concrete.

          Unfortunately, the
        • by Incadenza (560402)
          A house built with ICF has superior insulating properties (and does a fair job of blocking wifi signals too ;)

          Indeed, just yesterday there was an article about this in the Dutch papers. More and more people are complaining about dropped GSM reception and no digital TV reception after there houses have been renovated. Where the most striking case is the appartment block where they used aluminium panelling to cover the outer walls.

        • Re:Wooden houses? (Score:4, Interesting)

          by Sique (173459) on Sunday December 10, 2006 @06:56AM (#17183336) Homepage
          I wonder why my European parents have a wooden house (wooden frame filled with stone wool and covered with wooden planks, built in 1998), why their neighbours save one have also wooden frame houses, the oldest one being from 1654 (yeah, that's more than 350 years ago), why 25% of Germany's area is covered by forests, why Europe is in fact increasing its forest area, why towns like Quedlinburg or Erfurt are declared UNESCO cultural inheritance for their timber frame town centres, where all those pittoresce Black Forest and Bavarian rural houses come from, why we talk about "balconies" (which is just the german word Balken = timber).

          Wood is a very common material in residential construction in Germany, and in fact its usage has increased with the larger number of prebuilt houses being built here.
        • In northern europe, the situation is pretty much reversed. In norway the majority of houses are built out of wood. As are they in the parts of sweden and finland I've been to.

          I imagine this is because of wood beeing much more available (plenty of forests here, but it would be expensive to transport enouch wood for a house to central/south europe) and brick or concrete beeing harder and/or more expensive to insulate against the winter cold. As insulation becomes better/cheaper the ratio of wood to brick sh

          • Replying to myself here with another bit of information.

            Another reson why wood may be preferable in cold climates is the expanding and contacting of materials from different temperatures (think 50 celcius or 122 fahrenheit difference between inside and outside). A rigid brick or concrete structure would be more suceptible to cracking than a more flexible wooden one.

      • by ramsun (62627)
        Besides, what is going to hold up your concrete second floor? Or is it that all houses in your country have no cellars or second floors? The cost of constructing a house made entirely of mortar, brick, and stone is immense. Thus, wooden houses.

        This must be a regional thing. It's exactly the opposite in India, for example. Wooden houses (or at least wood paneled and floored houses) are for the rich, and the middle class live in concrete boxes. And yes, second, third and whatever floors are reinforced concret
        • by c_forq (924234)

          Sometimes the walls are also poured concrete, though nowadays they tend to be hollow concrete blocks. Makes it hell to deploy wireless networking - you need routers in every room.

          If you have a router in every room... don't you need a wire going to that router in every room? And if you have a wire going to every room, why are you bothering with wireless?
      • Re: (Score:2, Insightful)

        by kanweg (771128)
        In the Netherlands, most houses are concrete/brick based. And they are very energy efficient, because there are two walls, the space between them being filled with insulating foam.

        Bert
      • I would be hard pressed to find a recent building (less than 200 years old) which is not in cut stone, concrete, brick, or parpaing (concrete already made in the form of a big brick with a empty room in the middle). Sure there are *some* wood house, for example in some region near the german/french frontier, old house which are built with wooden raster and some sort of filling, generally they are "kept" as historical heritage. Maybe also those garden pavillion. But the rest , the bulk, is definitively not i
      • I live in Tenerife, a Spanish territory off the West coast of Africa... Houses here are all block and concrete, with tiled floors. The floors are poured concrete too.

        Back in the UK most houses are built out of brick with wooden floors, but more modern buildings tend to have an absence of wood. In the UK however floors tend to be carpeted. There's not a problem with brick walls as they're all made of two walls with insulating in the middle, so they're actually quite warm in the winter.

        For me, a chap from Eng
      • by pjt33 (739471)
        Besides, what is going to hold up your concrete second floor?
        Steel-reinforced concrete.
        The cost of constructing a house made entirely of mortar, brick, and stone is immense.
        Ten to twenty thousand USD in Ecuador. Of course, materials and labour are both more expensive in the US, but I still suspect that the land is the real expense.
      • by Ihlosi (895663)
        It can't be fun, so the solution is to build a brick exterior and set up a wooden insulated studwall on the interior.

        That's a stupid solution. Who taught you that ?P
        The point of insulation is to move the dew point as far to the _outside_ of the wall as possible, since you don't want to have water condensating on the inside of your concrete wall and turn it into a mildew farm. The way to do this is by insulating the brick walls on the _outside_, not on the inside. Slap 15-20 cm of insulation on the outside

      • by hcdejong (561314)
        Sad thing is, mansonry conducts heat. While some regions might not consider this a problem, try living in a brick house when the temperature drops below 0 farenheight. It can't be fun, so the solution is to build a brick exterior and set up a wooden insulated studwall on the interior.

        Yes, we use double walls. The exterior is brick. The interior can be another layer of brick, or some form of concrete, often lightweight porous concrete blocks. These blocks are large (30x50x8 cm) so you can build a wall much q
        • by Ihlosi (895663)
          Yes, we use double walls. The exterior is brick.

          You'd do that only if you want the bricks to be visible on the outside. If you don't care about that, just insulate the outside of the wall ... that's it.

          Also, remember that most bricks in the US aren't the somewhat hollow type that's used over here, which has quite good insulating properties, but solid bricks which conduct heat quite well.

  • Really, though, what did you expect from Texas?

    Link [chicagotribune.com]

    The only people in the case with a conscience are the jurors, the prosecutor and the judge had no qualms. That's not really a surprise though, not too many defense attorneys become judges. In fact, the more people you imprison as a prosecutor, the better your chance to become a judge or hold public office - this combined with prosecutorial immunity - and the fact that charges are rarely filed against prosecutors who engage in clearly illegal behavior such a
    • by Don Negro (1069) *
      As a seventh-generation Texan*, I expect a hell of a lot more.

      *On the Anglo side; no one ever counts the Comanche...
    • I passed the parent on to a friend of mine who happens to be a DA with 20+ years experience in a major southern California jurisdiction. I got the following reply:

      1. Prosecutors who do things like destroy evidence get fired and disbarred. Even in Texas. There are canons of ethics, business codes and bar rules for every jurisdiction, that impose on prosecutors the duty to "do justice", representing the interests of all the residents of the jurisdiction, including the accused. Do individual prosecuto
      • by b0s0z0ku (752509)
        1. Prosecutors who do things like destroy evidence get fired and disbarred.


        Not only that. In NJ, and I suspect other states as well, perjury or deliberate misconduct resulting in execution is a capital offense. So the prosecutor might actually find himself on the other side of the walls.


        -b.

  • by creimer (824291) on Sunday December 10, 2006 @02:02AM (#17182222) Homepage
    Tried reading the article but my Sony laptop caught on fire.
  • by harlows_monkeys (106428) on Sunday December 10, 2006 @02:41AM (#17182406) Homepage
    It's not just arson investigation where there has been a lot of junk science (or no science). For a long time, the FBI was using analysis of the alloy composition of bullets to see if two bullets came from the same box of bullets. Their belief was that there were variations over time in manufacture, and so that if two bullets (say, one taken from a victim, and one taken from a suspect) had very similar composition, they came from the same box (and so, presumably the suspect once owned the bullet taken from the victim).

    After something like 40 years of this being accepted, someone actually tested it. Result: no freaking correlation at all. The variation in composition of bullets within a given box was the same as variation among bullets from different boxes, purchased years apart. This is a completely worthless forensic technique.

    Or consider early DNA testing. Up until at least the mid '90s (I don't know what they do now) a DNA test only looked for matches at a small number of base pairs. For any given DNA sample tested, there would be thousands of people in the world that matches that sample. What this meant was the the scientifically correct way to use DNA testing was to find your suspects using traditional police techniques, and THEN use a DNA test. If you had, say, 3 good suspects, and one of them had a DNA match, then that was very good evidence against that suspect. Unfortunately, sometimes it was used the other way. They'd start with the DNA, match it against whatever samples they had on file, and if they got a match, they'd go after that person. That's bogus.

    If you look into the science behind much police investigation, you get this strange feeling you've fallen through some kind of wormhole and gone back to the early 19th century. It's amazing how much in common use has not been rigorously tested and peer reviewed by real scientists.

    • It's amazing how much in common use has not been rigorously tested and peer reviewed by real scientists.

      What do forensic scientists do, then? Are they mostly concerned with chemical analyses kits and ballistics? This isn't a troll--I honestly don't know what they would do if not validate techniques and processes--like what medical researchers spend so much time doing.
      • by Big Bob the Finder (714285) * on Sunday December 10, 2006 @03:13AM (#17182556) Homepage Journal

        Things can get tricky here. It can be a bit like sculpture, in a way- if you chisel your evidence just the right way, maybe it'll look like what you want. That can be a very bad thing. However, some investigations require tailor-made tests; I can think of a couple instances- none of which had anything to do with trying the accused, fortunately- that I was called upon to create a test or an experiment that produced results that could be used to determine an association. For example, when the accused was found with certain components, I was asked to determine if those components could be used to detonate a certain kind of bomb. They weren't used in the trial, but they were used to hold the suspect in pre-9/11 America when you had to prove that sort of thing.

        Some tests rely upon the odds of producing a match- as with fingerprints. However, these are not always reliable. [wikipedia.org] That's biometrics, with a long and sometimes dubious track record. I'm not even sure if there's been a paper in the refereed literature that cites the statistics on the likelihood of a match between two non-related prints given a certain number of features.

        Other fields, such as firearms and toolmarks, are even more open to interpretation. DNA evidence is a little better in some regards, but these figures have been botched, too- sometimes with lab accidents, sometimes intentionally. Fortunately, standards have gotten a lot tighter, and DNA evidence has been used to exonerate a considerable number of the accused, including a distressing number of individuals on death row.

        Fortunately, some are straightforward. While that field test for, say, cocaine might give a false positive for several hundred (or thousand) compounds, the Raman infrared spectrometer can tell you what it is, even through the polyethylene bag in which the sample is kept. Then another test- gas chromatography or gas chrom with a mass spec detector (GC/MS) is used to confirm. The chemistry side of it is pretty good, provided orthogonal analysis- two independent tests based on different principles of analysis- can demonstrate that the sample has been identified correctly.

    • by dbIII (701233)
      For a long time, the FBI was using analysis of the alloy composition of bullets to see if two bullets came from the same box of bullets.

      Come on - these guy use polygraphs - junk science took them over decades ago. If you look at things internationally it isn't so bad. I'll bet your state police don't go in for voodoo detection either.

      • Re: (Score:3, Funny)

        by Fred_A (10934)
        Come on - these guy use polygraphs - junk science took them over decades ago.
        Not to mention that according to the US TV shows sold over here, about 1/4th of their agents appear to be psychics of a kind or another too. Is there a budget line for dribbling candles, pendulums and pentagram chalks ? ;)

  • Fire investigation (Score:3, Interesting)

    by Big Bob the Finder (714285) * on Sunday December 10, 2006 @02:53AM (#17182468) Homepage Journal

    What is probably the single most annoying thing about fire investigation- from the investigator's perspective- is that arson is a terribly difficult crime to prove. Without a witness or some form of photographic or video evidence where an individual physically lights something on fire, the crime of arson is difficult to prove. As an instructor long ago put it to us: A man walks into a structure, and then walks back out. Later, it catches on fire. Houses burn all the time- bad wiring, gasoline stored near a gas water heater, cigarettes left burning. But causality- that that fire was intentionally set, and was set by that individual- may be difficult to prove.

    In that regard, arson can be more difficult to prove than murder. With murder, there is frequently trace evidence with everything from blood droplets to weapons used, that can associate the murderer with the crime. With arson, in many cases there is heavy fire, smoke, and water damage, as well as the difficulty in proving that a fire started intentionally versus accidentally. Trace evidence such as gasoline found on the shoes of the accused arsonist can often be explained by more mundane events, such as spills at a filling station.

    Making things worse, the folks who investigate are often poorly- or incorrectly- trained, and sometimes don't even want the job. Things are changing and candidates are frequently better educated than they have been in the past, but it's still a little rough around the edges. There aren't too many investigators in the field with advanced degrees, and a week or two of schooling (Arson I and II) at a state fire academy or the National Fire Academy are considered enough to get to work in many cases. 40 hours of fire investigation training, and you can help in putting people behind bars for what is considered a heinous crime such as arson of a habitable structure.

    Sometimes investigation doesn't even start with the fire itself. Financial records are often scrutinized to determine if the accused would benefit financially. Business not doing well? Maybe it was torched. Home being remodeled? Maybe a convenient excuse to collect on insurance because of some major construction issues that existed. Upside down in your auto loan and gas hit $3 a gallon? That Yukon sure burns good!

    Put all these together, and it's little wonder that some of the folks accused and convicted of this sort of thing are convicted and jailed. Many are poor, and get lousy lawyers- juries are likely to convict on scant evidence when the alternative is to let a possible firebug out on the streets.

    Fortunately, there are improvements, and the standards for training have gone way the heck up in past years. Certification under some standard for training is often required for the job, as well as continuing education to stay on the job. Engineers, chemists, modelers, and physicists tackle some of the more difficult issues with lab tests to back up what's being said in court. It's one thing to say that a steam pipe at X degrees for Y years can eventually cause enough pyrolysis of nearby wood to create open flame; it's another to have some PhD back it up with experiments that prove it, possibly exonerating the accused.

    Sometimes folks believe strange things from way the heck back in their training. This is part of the legend behind "spontaneous human combustion." The '921 says in it somewhere in a straightforward (and vaguely comforting) manner that humans do not spontaneously combust. Now only if we can do that with the other bits of legend that investigators have clung to over the ages.

  • Here is some interesting information from a book on my shelf on Arson:

    From: Fire Investigation; DAÉID, NIAMH NIC; CRC Press, Boca Raton, FL, USA, 2004. ISBN: 0-415-24891-4

    (Excerpt: Chapter 1)

    A fire develops through a number of fairly predictable stages. Initially a source of ignition is required at a site suitable for flaming combustion to occur. The materials begin to burn in a sustained ignition with an open flame which remains once the initial source of ignition is removed. This ignition is l

    • by Fred_A (10934)
      Damn... my "Arson for Dummies" doesn't mention any of this... I knew I should have gotten something more serious... ;)
  • Regrettably, this doesn't come as a surprise. In my own field we have the example of "voiceprint analysis", where "analysts" claimed to be able to identify a suspect's voice by comparing two spectrograms. This was complete and utter nonsense. There was no evidence that human beings have unique voices, no underlying theory of differences among voices (since almost all research focussed on abstracting away from individual differences so as to understand the acoustic basis for speech perception), no published

  • My father was the arson investigator in my home town (may he rest in peace), and I joined the fire department when I turned 18. I've been on dozens of investigations with him, and I have NEVER heard him say conclusively that an accelerant was used in any fire without having some kind of evidence to back it up. We regularly took samples from suspect areas and sent them to the county arson/bomb lab for analysis. My father taught me many things about fires and arsons, and the only thing I remember him saying t
  • by Bertie (87778) on Sunday December 10, 2006 @05:59AM (#17183160)
    Many of you across the pond won't be familiar with this disaster, but it's as good an example of fire spreading quickly without accelerants as you'll ever see. It all started when someone dropped a cigarette, and within a few minutes a hundred-metre long wooden stand was a goner, killing dozens of people. There's a video [youtube.com] of it on YouTube, although I should warn you that there's one or two scenes in it which I personally find slightly difficult to watch.
  • ...I was just arson about!
  • by JetScootr (319545) on Monday December 11, 2006 @04:58AM (#17192294) Journal
    I trained in 1979ish and then they were teaching how to fight flashover. One exercise involved a fully-involved brick "bedroom". Flames were up to the ceiling and spread across the entire room. The test: Put out the fire with a 1-2 second wide spray from a 2 1/2 inch hose. That's about 10-20 gallons of water.
    The trick is don't spray the hay, spray the ceiling over the hay - that's where the heat is. This is opposed to the conventional technique of spraying "the base" of the fire.
    The near-explosive boiling of water to steam takes away a coupla hundred degrees of temprature, and the sudden increase in humidity reduces the flame potential of aerable fuels like cloth, blankets, hay, etc ("aerable" as opposed to dense fuels like solid wood). The snuff-out is impressive.
    I don't think the article is right about this being "new", although it's possible the info spread slowly in different regions.
    • by ab762 (138582)
      Could you explain why "hay" is found in a "bedroom"? Is it used as a simulation of a mattress?

      It seems a substantially unrealistic exercise; few North American interiors have exposed brick.

      • Duh. Normally, hay is not found in a bedroom in any sizeable quantities. Brick walls were used so the fire school didn't have to build a new house for every exercise. Hay was used to simulate the semi-dense fuels commonly found in houses, such as furniture, beds, etc. Hay is a more realistic simulation than gasoline, liquid oxygen, basalt, etc.

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