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Fire investigation was historically plagued by myths like "concrete spalling means the floor was soaked in gasoline before being set on fire". Turns out, concre

Fire investigation was historically plagued by myths like "concrete spalling means the floor was soaked in gasoline before being set on fire". Turns out, concrete just does that whenever it gets very hot, with or without an accelerant.

arrosenberg 4y ago
Ironically, Law and Order SVU has an entire episode focused on that issue.
aidos 4y ago
This was posted years ago on HN and it has always stuck with me. https://www.newyorker.com/magazine/2009/09/07/trial-by-fire https://www.newyorker.com/magazine/2009/09/07/trial-by-fire
- UncleMeat 4y ago
  Jesus Christ. Death penalty advocates always say there are so many checks and that only absolute monsters are executed but this is a case made off animal spirits and the testimony of a fellow prisoner, both of which were later called into serious question. What the fuck. I think that a lot of people are just bloodthirsty and once they’ve categorized somebody as evil then anything can be done to them. Unbelievable.
  - ehecatl42 4y ago
    > animal spirits *mineral spirits But thanks! "Animal spirits" intrigued me, so I read the entire article. A clusterfuck from top to bottom, particularly the bit about the cracked glass patterns... something better explained by thermal shock of cold water from fire-hoses on hot glass, and not the use of BBQ lighter fluid as an accelerant. Haunting words: "I almost sent a man to die based on theories that were a load of crap."
    - UncleMeat 4y ago
      I used the term "animal spirits" to describe the voodoo that the arson investigator used to justify the conviction (I admit this is confusing given that "mineral spirits" plays a role in the article). The term is often used in economics to describe the fickle and unknowable and seemingly random reasons for market motion. This arson investigation feels just as random.
eftychis 4y ago
Oh That was a thing? Was/is there any actual expert involved ever in these claims? I am more worried about all the claims that one field expert can look at someone and tell if they are drunk, using specific substances or had a head trauma. Doctors can’t do that but I guess… there are “experts.”
- knodi123 4y ago
  Hell yes. A probably-innocent man in Texas executed for murdering his family, based primarily on the evidence of fire analysis which was later shown to be almost entirely bullshit. https://deathpenaltyinfo.org/policy-issues/innocence/executed-but-possibly-innocent#Cameron_Willingham https://deathpenaltyinfo.org/policy-issues/innocence/execute...
  - eftychis 4y ago
    This is so sad in so many ways. I had to research the topic and this was the first case popping up. Thank you, and... I am still really sad...
  - ghastmaster 4y ago
    > Ultimately, the authorities concluded that Willingham was a man without a conscience whose serial crimes had climaxed, almost inexorably, in murder. This is what has condemned innocents throughout history to death, torture, and prison. His history is what got him convicted, in my opinion. So many people forget to shield themselves from future indictment by acting "normal" in the present.
- duskwuff 4y ago
  > That was a thing? Was/is there any actual expert involved ever in these claims? Unfortunately, a lot of fire source experts were trained based on a mishmash of folk theories about arson, many of which have been subsequently disproven by scientific testing. There have been some improvements over the last decade or two, but the field is still heavily contaminated by junk science.
- ok_dad 4y ago
gerdesj 4y ago
Concrete spalling doesn't require fire at all. Ask any Civil Engineer (I'm not actually Chartered). I trained as a Civ Eng in Plymouth (Devon, UK) and obviously ended up in IT (22 years as MD of an IT firm). It's quite wet, windy and the air is pretty salty in Plimuff. All of those factors scream: Bad for conc. if you don't allow for them. Also, steel is well known to get quite unhappy in the presence of salty water, if it isn't cared for properly. Concrete cancer is another exciting opportunity to contend with in the face of ... conditions. Concrete is a marvellous material, it really is but it is a sodding complicated matrix of variously graded (sizes) stones (aggregate) and particular sands bound up in the cement plus some admixtures (stuff added for various reasons). The cement alone is properly complicated - clinker and that. When you mix the stuff up and pour it, it's a chemical reaction that happens and not simply drying. That's why it works underwater - what you are worrying about underwater is avoiding the finer materials being carried off before the stuff sets. In the air, you worry more about temperature effects on setting and wind causing the surface to dry too fast. The reaction is caused by water, so if the surface dries out, the reaction doesn't happen and you get ... spalling later in life. I hope that the studies quoted in court relating to conc spalling, describe the precise conditions that the stuff was poured in. Care will be taken over the effects of admixtures and the temperatures, weather and other conditions that affect setting and curing of conc. Was gap grading of the agg. a factor perhaps? What is the agg. composition anyway, let alone its size distribution? I could go on a lot, lot more and I'm not even close to being an expert. I can pour a decent 3-2-1 mix and expect it to do the job at home. My little DIY conc related projects tend to work rather well - my garden is quite challenging topographically. I hope I'm getting across that concrete is rather complicated. It's not a simple material just as balsa and elm are both "wood" but have very, very different properties.

arrosenberg 4y ago

Ironically, Law and Order SVU has an entire episode focused on that issue.

aidos 4y ago

This was posted years ago on HN and it has always stuck with me. https://www.newyorker.com/magazine/2009/09/07/trial-by-fire https://www.newyorker.com/magazine/2009/09/07/trial-by-fire

UncleMeat 4y ago
Jesus Christ. Death penalty advocates always say there are so many checks and that only absolute monsters are executed but this is a case made off animal spirits and the testimony of a fellow prisoner, both of which were later called into serious question. What the fuck. I think that a lot of people are just bloodthirsty and once they’ve categorized somebody as evil then anything can be done to them. Unbelievable.
- ehecatl42 4y ago
  > animal spirits *mineral spirits But thanks! "Animal spirits" intrigued me, so I read the entire article. A clusterfuck from top to bottom, particularly the bit about the cracked glass patterns... something better explained by thermal shock of cold water from fire-hoses on hot glass, and not the use of BBQ lighter fluid as an accelerant. Haunting words: "I almost sent a man to die based on theories that were a load of crap."
  - UncleMeat 4y ago
    I used the term "animal spirits" to describe the voodoo that the arson investigator used to justify the conviction (I admit this is confusing given that "mineral spirits" plays a role in the article). The term is often used in economics to describe the fickle and unknowable and seemingly random reasons for market motion. This arson investigation feels just as random.

eftychis 4y ago

Oh That was a thing? Was/is there any actual expert involved ever in these claims? I am more worried about all the claims that one field expert can look at someone and tell if they are drunk, using specific substances or had a head trauma. Doctors can’t do that but I guess… there are “experts.”

knodi123 4y ago
Hell yes. A probably-innocent man in Texas executed for murdering his family, based primarily on the evidence of fire analysis which was later shown to be almost entirely bullshit. https://deathpenaltyinfo.org/policy-issues/innocence/executed-but-possibly-innocent#Cameron_Willingham https://deathpenaltyinfo.org/policy-issues/innocence/execute...
- eftychis 4y ago
  This is so sad in so many ways. I had to research the topic and this was the first case popping up. Thank you, and... I am still really sad...
- ghastmaster 4y ago
  > Ultimately, the authorities concluded that Willingham was a man without a conscience whose serial crimes had climaxed, almost inexorably, in murder. This is what has condemned innocents throughout history to death, torture, and prison. His history is what got him convicted, in my opinion. So many people forget to shield themselves from future indictment by acting "normal" in the present.
duskwuff 4y ago
> That was a thing? Was/is there any actual expert involved ever in these claims? Unfortunately, a lot of fire source experts were trained based on a mishmash of folk theories about arson, many of which have been subsequently disproven by scientific testing. There have been some improvements over the last decade or two, but the field is still heavily contaminated by junk science.
ok_dad 4y ago

gerdesj 4y ago

Concrete spalling doesn't require fire at all. Ask any Civil Engineer (I'm not actually Chartered). I trained as a Civ Eng in Plymouth (Devon, UK) and obviously ended up in IT (22 years as MD of an IT firm). It's quite wet, windy and the air is pretty salty in Plimuff. All of those factors scream: Bad for conc. if you don't allow for them. Also, steel is well known to get quite unhappy in the presence of salty water, if it isn't cared for properly. Concrete cancer is another exciting opportunity to contend with in the face of ... conditions. Concrete is a marvellous material, it really is but it is a sodding complicated matrix of variously graded (sizes) stones (aggregate) and particular sands bound up in the cement plus some admixtures (stuff added for various reasons). The cement alone is properly complicated - clinker and that. When you mix the stuff up and pour it, it's a chemical reaction that happens and not simply drying. That's why it works underwater - what you are worrying about underwater is avoiding the finer materials being carried off before the stuff sets. In the air, you worry more about temperature effects on setting and wind causing the surface to dry too fast. The reaction is caused by water, so if the surface dries out, the reaction doesn't happen and you get ... spalling later in life. I hope that the studies quoted in court relating to conc spalling, describe the precise conditions that the stuff was poured in. Care will be taken over the effects of admixtures and the temperatures, weather and other conditions that affect setting and curing of conc. Was gap grading of the agg. a factor perhaps? What is the agg. composition anyway, let alone its size distribution? I could go on a lot, lot more and I'm not even close to being an expert. I can pour a decent 3-2-1 mix and expect it to do the job at home. My little DIY conc related projects tend to work rather well - my garden is quite challenging topographically. I hope I'm getting across that concrete is rather complicated. It's not a simple material just as balsa and elm are both "wood" but have very, very different properties.