9 ms·

I'd be curious to see a list of all of the classic cinema police cliche's that have no basis in evidence. So far there's the lie detector, blood spatter analysi

I'd be curious to see a list of all of the classic cinema police cliche's that have no basis in evidence. So far there's the lie detector, blood spatter analysis, bite marks.. what else?

JoeAltmaier 4y ago
Wait - blood spatter must follow the rules of physics, so there is some kind of analysis that would be valid, surely? Reading online I see its still respected lots of places and still taught in forensics. Don't know where that came from.
- agf 4y ago
  I think if you read this article you'll see (at least part of) the answer. Not only does a given action have to cause a definable result, the medium upon which the result is deposited has to provide enough detail to read the result back off it, and the people reading the result have to be able to be consistent and accurate in their analysis of that result. With bite marks, the skin has to hold the bite mark (which it doesn't) and experts have to be able to map it back to real human teeth (which they can't). With blood spatter, there are analogous problems.
  - JoeAltmaier 4y ago
    Which sounds miles from 'have no basis in evidence'. So that might have been a little hyperbolic.
    - snapcaster 4y ago
      I'm not sure why you're trying to play devil's advocate on that. The things they are claiming about the analysis techniques literally have no basis in evidence. Saying "blood spatters follow laws of physics" has nothing to do with what the experts are doing now
      - JoeAltmaier 4y ago
        ...and I countered with "the physics surely have validity", which the plentiful science done to date has corroborated. Not playing devil's advocate; just doing some simple searches and calling out hyperbole. These days folks have replaced science with advocacy. You know, that thing lawyers do to convince a jury. To the point folks think that you can arrive at a conclusion with advocacy. Instead of looking at the data. I'd ramble on about how the world is going to pot, because folks thing a sarcastic remark or clever-sounding turn of phrase is 'just as good' as facts. But oh well.
        snapcaster 4y ago
        "Blood spatter analysis" is not a physics based discipline. The other comment responding to you with the analogy about astrology is good explanation of what is wrong with your reasoning
        kortilla 4y ago
        You confused the GP statement about “blood spatter analysis” with a statement about “blood spatter”. If someone critiques astrology you don’t reply that “planets follow physics”.
    - ouid 4y ago
      not so, if i square a number, and get 4, There is no basis in evidence for the claim that the number I squared was 2. it could equally likely have been -2. Science is capable of making no stronger a claim than that.
- d1sxeyes 4y ago
  I think the key challenge to blood spatter analysis is not that there's no way it could be valid, it's that so far, it's based primarily on unsupported assumptions and statements. Those assumptions may well be correct, but the hard physics behind it has not been done yet, it's been just folks saying 'well I'm very clever and this is what I think'.
  - JoeAltmaier 4y ago
    An internet search shows there is research done, particularly the 'hard physics' behind it..
    - meheleventyone 4y ago
      Is there? Simulating forward sounds doable. Some fluid sprayed from here, with this mass and so on it lands as so. Backwards from a spatter pattern on an object sounds a lot harder, not least because there will be multiple possible answers and heaps of unknown variables.
- DSMan195276 4y ago
  I mean the Wikipedia article on it basically says as much: https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis > The validity of bloodstain pattern analysis has been questioned since the 1990s, and more recent studies cast significant doubt on its accuracy. A comprehensive 2009 National Academy of Sciences report concluded that "the uncertainties associated with bloodstain pattern analysis are enormous" and that purported bloodstain pattern experts' opinions are "more subjective than scientific." The report highlighted several incidents of blood spatter analysts overstating their qualifications and questioned the reliability of their methods. In 2021, the largest-to-date study on the accuracy of BPA was published, with results "show[ing] that [BPA conclusions] were often erroneous and often contradicted other analysts." That's not the same as saying it could _never_ be done properly, but the analysis being done right now is not that, even though it's presented in courts as expert opinion with high certainty.
- deleted 4y ago
  [deleted]
- etempleton 4y ago
  Blood splatter is still studied. What I think most forensic experts would tell you is they are really trying to compile as much evidence as possible that allows the largest reconstruction of what may have happened. It is not like the movies, or it shouldn’t be, where you find a single finger print and that determines who the killer is.
- cool_dude85 4y ago
  Everything follows the rule of physics. The existence of some way to do something is a very low bar to clear. There may be some way to determine if there's water underground, but that doesn't mean a dowsing rod can.
- tsimionescu 4y ago
  The actual current practice of blood spatter analysis is to the physics of blood splatters roughly what astrology is to the physics of the movement of stars and planets. Could there be an astronomy equivalent for blood spatter analysis? In principle yes, but it doesn't exist yet. Could the current astrology sometimes shed real light? In some cases yes, just like even an astrologer can tell you something true about where Mercury is likely to be on the sky tomorrow. But the vast majority of the claims of current experts are going to make claims a lot stronger than that. And just like most astrologers, they will make those claims based on what they want to be true, or what they think you want to be true, not on what the evidence tells them.
- pfortuny 4y ago
  Usually solving a PDE “backwards” is not possible. And that is exactly what those people are claiming to do. IE: from a specific (discrete) distribution of temperatures in, say a length of wire, you cannot infer the distribution some time before.
cscheid 4y ago
From my understanding, fingerprint analyses don't have widely-accepted specificity or sensitivity rates either. Those "73% match" figures are not derived from any sound principles.
TotoHorner 4y ago
Breathalyzer tests are incredibly inaccurate and prone to false-positives. Not saying they have no basis in evidence, but people drastically overestimate their accuracy.
- JoeAltmaier 4y ago
  They have an accuracy rate that is pretty good. Sure they have false-positives (eat a gas station pizza, ping positive) but far more likely are false-negatives due to bad air sampling. Folks go to all sorts of extremes to fake them in the car-installed devices e.g. have somebody else blow; blow through a long tube so the sample is just what's in the tube; hold it out the window and let the wind 'blow' into it; put two straws into a half-full drink cup, blow into one and connect the device to the other, and on and on. The devices have all sorts of countermeasures now including a dash-cam, temperature sensors, humidity sensors etc to try and ensure its actually the right human's breath.
  - TotoHorner 4y ago
    "Pretty good" is completely unacceptable if states will suspend your drivers license for 12 months if you refuse to take the breathalyzer test (many states do this).
    - deleted 4y ago
      [deleted]
    - kelnos 4y ago
      Yeah, it's gross that consent to a breathalyzer test is a precondition for even getting a license in the first place. Are people convicted of DUI based on breathalyzer evidence alone? I would hope that the breathalyzer is just used as a first gate (since it's relatively easy to administer), but then a conviction would require corroboration from a blood test. Then again, with our "justice" system as it is, I wouldn't be surprised if a breathalyzer is enough in some circumstances.
      - 4y ago
codeflo 4y ago
Lots of scandals around DNA evidence as well. It’s not the science itself that’s wrong, but mistakes can be made and were made during collection and in interpretation.
- amenghra 4y ago
  There’s also cases of people who received a transplant who then supposedly have two (or more) different DNAs in their blood.
  - throwaway894345 4y ago
    Wow, that's pretty crazy. I never really thought about how transplants imply two different sets of DNA cohabitating in the same body.
    - neaden 4y ago
      I think the relevant transplant is bone marrow, since that produces Red Blood Cells. Here is an article about it:https://www.nytimes.com/2019/12/07/us/dna-bone-marrow-transplant-crime-lab.html https://www.nytimes.com/2019/12/07/us/dna-bone-marrow-transp...
    - wahern 4y ago
      Pregnancy presents a similar situation, and fetal microchimerism among parous women is not uncommon. This also includes, supposedly, brain tissue: https://www.science.org/content/article/bearing-sons-can-alter-your-mind https://www.science.org/content/article/bearing-sons-can-alt...
    - jacobkg 4y ago
      A founder I worked with had both a bone marrow transplant and a lung transplant. He named his company 3dna to commemorate having three sets of DNA in his body
  - kstrauser 4y ago
    It also turns out that chimerism may be a lot more common than we’d thought.
rincewind 4y ago
hand-held laser speed measuring
paradisechris 4y ago
Fire pattern analysis often falsely claimed, from visual analysis alone, that fires were started with an accelerant.
Ekaros 4y ago
Body language experts... Thankfully I don't think it is used as evidence, but still...
- LtWorf 4y ago
  Think again.
duskwuff 4y ago
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.
av3csr 4y ago
This report is relevant. If I recall correctly it pointed that some of these analyses are not really reproducible. https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf
muaytimbo 4y ago
handwriting experts?
bolangi 4y ago
Fingerprint analysis is rather sketchy, convicting someone based on a tiny part of a print. Also lie detector analysis.
glenstein 4y ago
This was my first thought as well. I think penmanship analysis is a candidate.
- googlryas 4y ago
  There are two types of handwriting analysis - "Graphology" and forensic handwriting analysis. Graphology claims to be able to derive personality/psychological traits of the penman, and is just for charlatans. But, forensic handwriting analysis is "real" and useful, for determining if a known-author handwriting sample matches an unknown-author handwriting sample.
monocasa 4y ago
Hair analysis is another. Famously, a man was convicted based on hair at the scene that turned out to belong to a dog instead. https://splinternews.com/the-fbi-convicted-this-man-using-hair-analysis-it-was-1793847259 https://splinternews.com/the-fbi-convicted-this-man-using-ha...
DubiousPusher 4y ago
If only it was limited to the cinema. https://www.washingtonpost.com/local/crime/fbi-overstated-forensic-hair-matches-in-nearly-all-criminal-trials-for-decades/2015/04/18/39c8d8c6-e515-11e4-b510-962fcfabc310_story.html https://www.washingtonpost.com/local/crime/fbi-overstated-fo...
SV_BubbleTime 4y ago
Ballistic fingerprinting is almost completely nonsense as used in media. Has some real life use, but limited. There are multiple types. 1. Capturing a spent casing and comparing to a reference of that firearm. The idea being the primer indentation, and chamber wall tolerances/imperfections should let you match fired case to firearm. This was believed in so much that every firearm sold in the past 20 or so years in NY/MD/?? has required a spent case to be shipped with the gun and a case kept at some crime labs, or the owner is required to provide when registering the gun - the bullshit is that it doesn’t work at all - and not one single solved crime has ever been attributed to this system. Giant waste of money / feel good legislation. There is some correlation to be made… Factory Glocks have fairly unique square firing pins and it’s easy to say a case was or wasn’t fired from an unmodified Glock. Likewise, MP5 platform guns typically have fluted chambers and one can easily see the case marks on a fired case, but neither of these things will help with storing a sample. 2. Muzzle/barrel printing. While this is a LITTLE more scientific, mostly shit. For the most part, you need a really large flaw in a barrel to leave a matchable print on the barrel. You can look a fired bullet and easily tell the rifling. Polygonal (Glocks again), cut, button, hammer forged… but the whole microscope printing of miniature and unique imperfections is a lot more art than science. Again, easy to prove this bullet didn’t / couldn’t come from this gun - but hard to prove it came from this specific gun. 3. Micro stamping entirely bullshit. This is where a California despite overwhelming evidence it doesn’t work is still trying to get firing pins to leave a unique impression on the primer. The people that push for this stuff have no idea how guns work, never have.
- deleted 4y ago
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- bjt2n3904 4y ago
  Lived in MD. They did away with the spent shell casing law. Turns out they were literally throwing them unorganized into barrels. No way to organize or search through them if there was a need. Just a massive waste of taxpayer money.
efficax 4y ago
fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt). ballistic forensics only works if the gun is barely fired after the time that the bullets in question are fired, becuase each time you fire a gun it wears down the barrel again, in new ways. Fingerprint analysis is not based on solid science, nobody knows how common it is for someone to have very similar fingerprints to another person, and nobody knows what the right standard for "points of similarity" is. Fingerprint analysis has been used to convict people of crimes they could not have committed because they were not in the same state or even country, in ways that are provable: https://en.wikipedia.org/wiki/Brandon_Mayfield https://en.wikipedia.org/wiki/Brandon_Mayfield
- derefr 4y ago
  > fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt). I'm not a forensic technician, but I've watched probably every episode of every true-crime forensic documentary TV show / YouTube channel / podcast / etc that exists; which probably has some weak but non-negligible correlation with having a gestalt impression of what people do and don't use forensic techniques for in practice. (At least in the "solved" cases, since the point of these shows is "how they solved it.") In every use of "fiber analysis" I ever saw covered, where the "fiber analysis" was actually used to prove something, the thing they're always noticing is "trilobal fibers" — presumably because, at least for some period in recent history, those type of fibers only ever got used by specific manufacturers for specific use-cases (vehicle manufacturers, for car floor matting, IIRC); and weren't part of the composition of anything sold to individuals at retail (except, perhaps, replacement car floor mats.) So "trilobal fibers on the body" could be taken to imply "this person was at some point in a car footwell/trunk." I don't ever recall any case that made a "fiber analysis" claim other than that particular one. (Maybe once someone claimed something about what proprietary dyes were used on the fibers via GCMS assay — but that's not really "fiber analysis" per se.)
  - giantg2 4y ago
    I don't have a link handy, but there was a huge FBI scandle where their experts were essentially calling things a match to a specific person, etc. But yes, the science is fine if interpreted correctly. The correct phrasing would be exclude or not exclude a suspect. Or for your example, it could be consistent with someone having been in a vehicle. The problem is when the experts say they must have been in a vehicle, or especially a specific individual vehicle.
giantg2 4y ago
Many things do have a basis in science. The main problem (with almost all of them) is that the results are interpreted in incorrect ways. For example, you can compare hair and fibers just fine. You cannot say it's a match. You can only tell if it excludes or does not exclude someone. Yet many experts would say it's a "match" and the juries believe it's unique to the suspect.
hinkley 4y ago
Tracking calls that are over 60 seconds. Everything is electronic now. There are audit trails. It may take a while to figure out where you were, but they will. So the only advantage of getting off the phone early is to not be there when the cops show up. And the fact of where you were and what phone you used might help them identify you anyway.
eftychis 4y ago
You'd be surprised. a) Drug recognition experts -- commented that on a sibling comment too -- identifying drug usage vs e.g. trauma by sight. b) blood alcohol levels imply alcohol consumption -- you could actually be walking around with elevated alcohol levels not realizing it due to liver issues+yeast biome/diabetes (https://www.ncbi.nlm.nih.gov/books/NBK513346/ https://www.ncbi.nlm.nih.gov/books/NBK513346/) c) uniqueness of fingerprints -- studies pointing always this is a statistical argument not a unique identifier -- https://www.aaas.org/resources/latent-fingerprint-examination https://www.aaas.org/resources/latent-fingerprint-examinatio... d) partial DNA match implying perfect match -- partial matches have been used to convict people e) probably every depiction of mental illness -- there are exceptions but can't say Hollywood does its best there f) lawyer interaction -- no your lawyer can't just barge in: you have to ask specifically and probably persist on needing a lawyer to consider any further interaction. (And even how you word that is a minefield in the U.S.) g) talking to the police -- somehow invoking the fifth is something only bad guys do -- it is the other way around. And that is causing issues already. h) DNA, fingerprints imply you were there. No material can be moved around. And police knows that. (And of course substances too, e.g. you were in a tax/uber after someone exposed to X, you are now exposed to X.) i) pretty much all of statistics -- this case one would have hoped would be the eye opener (https://forensicstats.org/blog/2018/02/16/misuse-statistics-courtroom-sally-clark-case/ https://forensicstats.org/blog/2018/02/16/misuse-statistics-...) P.S. j) ... science honestly? I am always dumbfounded with how much lack of basic scientific knowledge plagues courts and in extend society. Courts can not survive with uncertainty: they have to make decisions and stick to them. Science is different.
- tinalumfoil 4y ago
  A lot of these problems come from deference to experts who wear the hat of science. For instance, https://en.wikipedia.org/wiki/R_v_Adams https://en.wikipedia.org/wiki/R_v_Adams a man was convicted because an expert said the DNA gave 1 in 200 million chance of incorrect match (or something similar), which is incorrect. I don't remember enough details to look it up, but I recall a US case where the prosecution repeatedly used an expert with a history of lying on stand and of course people wrongly spent time in jail for that. I think a bigger issue here, at least in the US, is prosecutions seems to have a really easy time finding experts, often on the same payroll as the prosecution, who say the things needed to get a conviction and jurors are encouraged to blindly trust that.
LtWorf 4y ago
This presents a summary of all the bullshit science. https://www.youtube.com/watch?v=ScmJvmzDcG0 https://www.youtube.com/watch?v=ScmJvmzDcG0
iudqnolq 4y ago
You want the book Junk Science and the American Criminal Justice System [1] by Chris Fabricant, the Innocence Project's Director of Strategic Litigation. The book is an approachable, anecdotal tour of some of the significant issues with each major sub-speciality within forensic science. The Innocence Project uses DNA testing to prove convicted criminals are actually completely innocent of everything, them undergoes the massive legal battle required to have a chance of going from conclusive evidence of innocence to release in the American Justice System. The are reasonable quibbles with their methods on the margin, but taken as a whole their work is an amazing contribution to society. Edit: I imagine some people might be skeptical that there's an uphill battle after conclusive evidence of innocence. Take a look at Shinn v Ramirez. Mark Brnovich, the Arizona Solicitor General, successfully convinced the Supreme Court to tell a federal judge they couldn't look at Ramirez's evidence he's innocent. Notably Brnovich said "innocence isn’t enough here" [2][3]. [1] https://www.amazon.com/Science-American-Criminal-Justice-System/dp/1636140300 https://www.amazon.com/Science-American-Criminal-Justice-Sys... [2] https://deathpenalty.org/innocence-isnt-enough-here-arizona-tells-scotus/ https://deathpenalty.org/innocence-isnt-enough-here-arizona-... [3] https://www.scotusblog.com/case-files/cases/shinn-v-ramirez/ https://www.scotusblog.com/case-files/cases/shinn-v-ramirez/
nonrandomstring 4y ago
"The Lie Behind the Lie Detector" had a big impact on me [1]. As a kid I made lie detectors (a 9 volt battery, 1M-Ohm resistor, BC108 transistor and buzzer) and got sent home from school for "Interrogating" the other kids. The teacher evidently thought it really worked - even though as an 8 year old I knew it was just an electronic trick. 40 years later the Iraqi government was purchasing thousands of ADE 651 "bomb detectors" [2] - basically a stick - that no doubt caused some poor dudes to get blown to bits by IEDs. All technology (indistinguishable from magic) has a cult-like aura around it, in that there's the reality of what it does, and a separate set of human beliefs about what it does. Cybersecurity is full of wishful and magical thinking in this regard. I sometimes feel like a kind of James Randi, trying to debunk the certainty people want and project on to technologies. [1] https://antipolygraph.org/lie-behind-the-lie-detector.pdf https://antipolygraph.org/lie-behind-the-lie-detector.pdf [2] https://www.cnet.com/culture/divining-rod-reborn-as-explosive-detection-device/ https://www.cnet.com/culture/divining-rod-reborn-as-explosiv...
- ghastmaster 4y ago
  Thank you. I had not heard of this product before. I want one. https://en.wikipedia.org/wiki/ADE_651 https://en.wikipedia.org/wiki/ADE_651 > According to Iraqi police officer Jasim Hussein, "The vast majority of the people we stop, it's because of their perfume". A fellow officer, Hasan Ouda, commented that "Most people now understand it's what gets them searched, so they don't use as much."
- hatsunearu 4y ago
  Ulgh, knowing the polygraph is a lie is actually a huge hazard for you. I once had to take a polygraph test, and I was freaking the fuck out because I knew being nervous will register me as a liar, and I wasn't actually lying at all. I tried my best to stay calm, but I was freaking out during the test, and I actually did fail the polygraph, but passed after a retest. It's such bullshit. I wish they got rid of this bullshit technology from this earth, because I had so much on the line and I was absolutely miserable before and during the test.
  - ok_dad 4y ago
hammock 4y ago
how is blood spatter analysis bogus?
WheatMillington 4y ago
Fire forensics.
deleted 4y ago
[deleted]

I'd be curious to see a list of all of the classic cinema police cliche's that have no basis in evidence. So far there's the lie detector, blood spatter analysis, bite marks.. what else?

JoeAltmaier 4y ago

Wait - blood spatter must follow the rules of physics, so there is some kind of analysis that would be valid, surely? Reading online I see its still respected lots of places and still taught in forensics. Don't know where that came from.

agf 4y ago
I think if you read this article you'll see (at least part of) the answer. Not only does a given action have to cause a definable result, the medium upon which the result is deposited has to provide enough detail to read the result back off it, and the people reading the result have to be able to be consistent and accurate in their analysis of that result. With bite marks, the skin has to hold the bite mark (which it doesn't) and experts have to be able to map it back to real human teeth (which they can't). With blood spatter, there are analogous problems.
- JoeAltmaier 4y ago
  Which sounds miles from 'have no basis in evidence'. So that might have been a little hyperbolic.
  - snapcaster 4y ago
    I'm not sure why you're trying to play devil's advocate on that. The things they are claiming about the analysis techniques literally have no basis in evidence. Saying "blood spatters follow laws of physics" has nothing to do with what the experts are doing now
    - JoeAltmaier 4y ago
      ...and I countered with "the physics surely have validity", which the plentiful science done to date has corroborated. Not playing devil's advocate; just doing some simple searches and calling out hyperbole. These days folks have replaced science with advocacy. You know, that thing lawyers do to convince a jury. To the point folks think that you can arrive at a conclusion with advocacy. Instead of looking at the data. I'd ramble on about how the world is going to pot, because folks thing a sarcastic remark or clever-sounding turn of phrase is 'just as good' as facts. But oh well.
      - snapcaster 4y ago
        "Blood spatter analysis" is not a physics based discipline. The other comment responding to you with the analogy about astrology is good explanation of what is wrong with your reasoning
      - kortilla 4y ago
        You confused the GP statement about “blood spatter analysis” with a statement about “blood spatter”. If someone critiques astrology you don’t reply that “planets follow physics”.
  - ouid 4y ago
    not so, if i square a number, and get 4, There is no basis in evidence for the claim that the number I squared was 2. it could equally likely have been -2. Science is capable of making no stronger a claim than that.
d1sxeyes 4y ago
I think the key challenge to blood spatter analysis is not that there's no way it could be valid, it's that so far, it's based primarily on unsupported assumptions and statements. Those assumptions may well be correct, but the hard physics behind it has not been done yet, it's been just folks saying 'well I'm very clever and this is what I think'.
- JoeAltmaier 4y ago
  An internet search shows there is research done, particularly the 'hard physics' behind it..
  - meheleventyone 4y ago
    Is there? Simulating forward sounds doable. Some fluid sprayed from here, with this mass and so on it lands as so. Backwards from a spatter pattern on an object sounds a lot harder, not least because there will be multiple possible answers and heaps of unknown variables.
DSMan195276 4y ago
I mean the Wikipedia article on it basically says as much: https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis > The validity of bloodstain pattern analysis has been questioned since the 1990s, and more recent studies cast significant doubt on its accuracy. A comprehensive 2009 National Academy of Sciences report concluded that "the uncertainties associated with bloodstain pattern analysis are enormous" and that purported bloodstain pattern experts' opinions are "more subjective than scientific." The report highlighted several incidents of blood spatter analysts overstating their qualifications and questioned the reliability of their methods. In 2021, the largest-to-date study on the accuracy of BPA was published, with results "show[ing] that [BPA conclusions] were often erroneous and often contradicted other analysts." That's not the same as saying it could _never_ be done properly, but the analysis being done right now is not that, even though it's presented in courts as expert opinion with high certainty.
deleted 4y ago
[deleted]
etempleton 4y ago
Blood splatter is still studied. What I think most forensic experts would tell you is they are really trying to compile as much evidence as possible that allows the largest reconstruction of what may have happened. It is not like the movies, or it shouldn’t be, where you find a single finger print and that determines who the killer is.
cool_dude85 4y ago
Everything follows the rule of physics. The existence of some way to do something is a very low bar to clear. There may be some way to determine if there's water underground, but that doesn't mean a dowsing rod can.
tsimionescu 4y ago
The actual current practice of blood spatter analysis is to the physics of blood splatters roughly what astrology is to the physics of the movement of stars and planets. Could there be an astronomy equivalent for blood spatter analysis? In principle yes, but it doesn't exist yet. Could the current astrology sometimes shed real light? In some cases yes, just like even an astrologer can tell you something true about where Mercury is likely to be on the sky tomorrow. But the vast majority of the claims of current experts are going to make claims a lot stronger than that. And just like most astrologers, they will make those claims based on what they want to be true, or what they think you want to be true, not on what the evidence tells them.
pfortuny 4y ago
Usually solving a PDE “backwards” is not possible. And that is exactly what those people are claiming to do. IE: from a specific (discrete) distribution of temperatures in, say a length of wire, you cannot infer the distribution some time before.

cscheid 4y ago

From my understanding, fingerprint analyses don't have widely-accepted specificity or sensitivity rates either. Those "73% match" figures are not derived from any sound principles.

TotoHorner 4y ago

Breathalyzer tests are incredibly inaccurate and prone to false-positives. Not saying they have no basis in evidence, but people drastically overestimate their accuracy.

JoeAltmaier 4y ago
They have an accuracy rate that is pretty good. Sure they have false-positives (eat a gas station pizza, ping positive) but far more likely are false-negatives due to bad air sampling. Folks go to all sorts of extremes to fake them in the car-installed devices e.g. have somebody else blow; blow through a long tube so the sample is just what's in the tube; hold it out the window and let the wind 'blow' into it; put two straws into a half-full drink cup, blow into one and connect the device to the other, and on and on. The devices have all sorts of countermeasures now including a dash-cam, temperature sensors, humidity sensors etc to try and ensure its actually the right human's breath.
- TotoHorner 4y ago
  "Pretty good" is completely unacceptable if states will suspend your drivers license for 12 months if you refuse to take the breathalyzer test (many states do this).
  - deleted 4y ago
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  - kelnos 4y ago
    Yeah, it's gross that consent to a breathalyzer test is a precondition for even getting a license in the first place. Are people convicted of DUI based on breathalyzer evidence alone? I would hope that the breathalyzer is just used as a first gate (since it's relatively easy to administer), but then a conviction would require corroboration from a blood test. Then again, with our "justice" system as it is, I wouldn't be surprised if a breathalyzer is enough in some circumstances.
    - 4y ago

codeflo 4y ago

Lots of scandals around DNA evidence as well. It’s not the science itself that’s wrong, but mistakes can be made and were made during collection and in interpretation.

amenghra 4y ago
There’s also cases of people who received a transplant who then supposedly have two (or more) different DNAs in their blood.
- throwaway894345 4y ago
  Wow, that's pretty crazy. I never really thought about how transplants imply two different sets of DNA cohabitating in the same body.
  - neaden 4y ago
    I think the relevant transplant is bone marrow, since that produces Red Blood Cells. Here is an article about it:https://www.nytimes.com/2019/12/07/us/dna-bone-marrow-transplant-crime-lab.html https://www.nytimes.com/2019/12/07/us/dna-bone-marrow-transp...
  - wahern 4y ago
    Pregnancy presents a similar situation, and fetal microchimerism among parous women is not uncommon. This also includes, supposedly, brain tissue: https://www.science.org/content/article/bearing-sons-can-alter-your-mind https://www.science.org/content/article/bearing-sons-can-alt...
  - jacobkg 4y ago
    A founder I worked with had both a bone marrow transplant and a lung transplant. He named his company 3dna to commemorate having three sets of DNA in his body
- kstrauser 4y ago
  It also turns out that chimerism may be a lot more common than we’d thought.

rincewind 4y ago

hand-held laser speed measuring

paradisechris 4y ago

Fire pattern analysis often falsely claimed, from visual analysis alone, that fires were started with an accelerant.

Ekaros 4y ago

Body language experts... Thankfully I don't think it is used as evidence, but still...

LtWorf 4y ago
Think again.

duskwuff 4y ago

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.

av3csr 4y ago

This report is relevant. If I recall correctly it pointed that some of these analyses are not really reproducible. https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf

muaytimbo 4y ago

handwriting experts?

bolangi 4y ago

Fingerprint analysis is rather sketchy, convicting someone based on a tiny part of a print. Also lie detector analysis.

glenstein 4y ago

This was my first thought as well. I think penmanship analysis is a candidate.

googlryas 4y ago
There are two types of handwriting analysis - "Graphology" and forensic handwriting analysis. Graphology claims to be able to derive personality/psychological traits of the penman, and is just for charlatans. But, forensic handwriting analysis is "real" and useful, for determining if a known-author handwriting sample matches an unknown-author handwriting sample.

monocasa 4y ago

Hair analysis is another. Famously, a man was convicted based on hair at the scene that turned out to belong to a dog instead. https://splinternews.com/the-fbi-convicted-this-man-using-hair-analysis-it-was-1793847259 https://splinternews.com/the-fbi-convicted-this-man-using-ha...

DubiousPusher 4y ago

If only it was limited to the cinema. https://www.washingtonpost.com/local/crime/fbi-overstated-forensic-hair-matches-in-nearly-all-criminal-trials-for-decades/2015/04/18/39c8d8c6-e515-11e4-b510-962fcfabc310_story.html https://www.washingtonpost.com/local/crime/fbi-overstated-fo...

SV_BubbleTime 4y ago

Ballistic fingerprinting is almost completely nonsense as used in media. Has some real life use, but limited. There are multiple types. 1. Capturing a spent casing and comparing to a reference of that firearm. The idea being the primer indentation, and chamber wall tolerances/imperfections should let you match fired case to firearm. This was believed in so much that every firearm sold in the past 20 or so years in NY/MD/?? has required a spent case to be shipped with the gun and a case kept at some crime labs, or the owner is required to provide when registering the gun - the bullshit is that it doesn’t work at all - and not one single solved crime has ever been attributed to this system. Giant waste of money / feel good legislation. There is some correlation to be made… Factory Glocks have fairly unique square firing pins and it’s easy to say a case was or wasn’t fired from an unmodified Glock. Likewise, MP5 platform guns typically have fluted chambers and one can easily see the case marks on a fired case, but neither of these things will help with storing a sample. 2. Muzzle/barrel printing. While this is a LITTLE more scientific, mostly shit. For the most part, you need a really large flaw in a barrel to leave a matchable print on the barrel. You can look a fired bullet and easily tell the rifling. Polygonal (Glocks again), cut, button, hammer forged… but the whole microscope printing of miniature and unique imperfections is a lot more art than science. Again, easy to prove this bullet didn’t / couldn’t come from this gun - but hard to prove it came from this specific gun. 3. Micro stamping entirely bullshit. This is where a California despite overwhelming evidence it doesn’t work is still trying to get firing pins to leave a unique impression on the primer. The people that push for this stuff have no idea how guns work, never have.

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bjt2n3904 4y ago
Lived in MD. They did away with the spent shell casing law. Turns out they were literally throwing them unorganized into barrels. No way to organize or search through them if there was a need. Just a massive waste of taxpayer money.

efficax 4y ago

fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt). ballistic forensics only works if the gun is barely fired after the time that the bullets in question are fired, becuase each time you fire a gun it wears down the barrel again, in new ways. Fingerprint analysis is not based on solid science, nobody knows how common it is for someone to have very similar fingerprints to another person, and nobody knows what the right standard for "points of similarity" is. Fingerprint analysis has been used to convict people of crimes they could not have committed because they were not in the same state or even country, in ways that are provable: https://en.wikipedia.org/wiki/Brandon_Mayfield https://en.wikipedia.org/wiki/Brandon_Mayfield

derefr 4y ago
> fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt). I'm not a forensic technician, but I've watched probably every episode of every true-crime forensic documentary TV show / YouTube channel / podcast / etc that exists; which probably has some weak but non-negligible correlation with having a gestalt impression of what people do and don't use forensic techniques for in practice. (At least in the "solved" cases, since the point of these shows is "how they solved it.") In every use of "fiber analysis" I ever saw covered, where the "fiber analysis" was actually used to prove something, the thing they're always noticing is "trilobal fibers" — presumably because, at least for some period in recent history, those type of fibers only ever got used by specific manufacturers for specific use-cases (vehicle manufacturers, for car floor matting, IIRC); and weren't part of the composition of anything sold to individuals at retail (except, perhaps, replacement car floor mats.) So "trilobal fibers on the body" could be taken to imply "this person was at some point in a car footwell/trunk." I don't ever recall any case that made a "fiber analysis" claim other than that particular one. (Maybe once someone claimed something about what proprietary dyes were used on the fibers via GCMS assay — but that's not really "fiber analysis" per se.)
- giantg2 4y ago
  I don't have a link handy, but there was a huge FBI scandle where their experts were essentially calling things a match to a specific person, etc. But yes, the science is fine if interpreted correctly. The correct phrasing would be exclude or not exclude a suspect. Or for your example, it could be consistent with someone having been in a vehicle. The problem is when the experts say they must have been in a vehicle, or especially a specific individual vehicle.

giantg2 4y ago

Many things do have a basis in science. The main problem (with almost all of them) is that the results are interpreted in incorrect ways. For example, you can compare hair and fibers just fine. You cannot say it's a match. You can only tell if it excludes or does not exclude someone. Yet many experts would say it's a "match" and the juries believe it's unique to the suspect.

hinkley 4y ago

Tracking calls that are over 60 seconds. Everything is electronic now. There are audit trails. It may take a while to figure out where you were, but they will. So the only advantage of getting off the phone early is to not be there when the cops show up. And the fact of where you were and what phone you used might help them identify you anyway.

eftychis 4y ago

You'd be surprised. a) Drug recognition experts -- commented that on a sibling comment too -- identifying drug usage vs e.g. trauma by sight. b) blood alcohol levels imply alcohol consumption -- you could actually be walking around with elevated alcohol levels not realizing it due to liver issues+yeast biome/diabetes (https://www.ncbi.nlm.nih.gov/books/NBK513346/ https://www.ncbi.nlm.nih.gov/books/NBK513346/) c) uniqueness of fingerprints -- studies pointing always this is a statistical argument not a unique identifier -- https://www.aaas.org/resources/latent-fingerprint-examination https://www.aaas.org/resources/latent-fingerprint-examinatio... d) partial DNA match implying perfect match -- partial matches have been used to convict people e) probably every depiction of mental illness -- there are exceptions but can't say Hollywood does its best there f) lawyer interaction -- no your lawyer can't just barge in: you have to ask specifically and probably persist on needing a lawyer to consider any further interaction. (And even how you word that is a minefield in the U.S.) g) talking to the police -- somehow invoking the fifth is something only bad guys do -- it is the other way around. And that is causing issues already. h) DNA, fingerprints imply you were there. No material can be moved around. And police knows that. (And of course substances too, e.g. you were in a tax/uber after someone exposed to X, you are now exposed to X.) i) pretty much all of statistics -- this case one would have hoped would be the eye opener (https://forensicstats.org/blog/2018/02/16/misuse-statistics-courtroom-sally-clark-case/ https://forensicstats.org/blog/2018/02/16/misuse-statistics-...) P.S. j) ... science honestly? I am always dumbfounded with how much lack of basic scientific knowledge plagues courts and in extend society. Courts can not survive with uncertainty: they have to make decisions and stick to them. Science is different.

tinalumfoil 4y ago
A lot of these problems come from deference to experts who wear the hat of science. For instance, https://en.wikipedia.org/wiki/R_v_Adams https://en.wikipedia.org/wiki/R_v_Adams a man was convicted because an expert said the DNA gave 1 in 200 million chance of incorrect match (or something similar), which is incorrect. I don't remember enough details to look it up, but I recall a US case where the prosecution repeatedly used an expert with a history of lying on stand and of course people wrongly spent time in jail for that. I think a bigger issue here, at least in the US, is prosecutions seems to have a really easy time finding experts, often on the same payroll as the prosecution, who say the things needed to get a conviction and jurors are encouraged to blindly trust that.

LtWorf 4y ago

This presents a summary of all the bullshit science. https://www.youtube.com/watch?v=ScmJvmzDcG0 https://www.youtube.com/watch?v=ScmJvmzDcG0

iudqnolq 4y ago

You want the book Junk Science and the American Criminal Justice System [1] by Chris Fabricant, the Innocence Project's Director of Strategic Litigation. The book is an approachable, anecdotal tour of some of the significant issues with each major sub-speciality within forensic science. The Innocence Project uses DNA testing to prove convicted criminals are actually completely innocent of everything, them undergoes the massive legal battle required to have a chance of going from conclusive evidence of innocence to release in the American Justice System. The are reasonable quibbles with their methods on the margin, but taken as a whole their work is an amazing contribution to society. Edit: I imagine some people might be skeptical that there's an uphill battle after conclusive evidence of innocence. Take a look at Shinn v Ramirez. Mark Brnovich, the Arizona Solicitor General, successfully convinced the Supreme Court to tell a federal judge they couldn't look at Ramirez's evidence he's innocent. Notably Brnovich said "innocence isn’t enough here" [2][3]. [1] https://www.amazon.com/Science-American-Criminal-Justice-System/dp/1636140300 https://www.amazon.com/Science-American-Criminal-Justice-Sys... [2] https://deathpenalty.org/innocence-isnt-enough-here-arizona-tells-scotus/ https://deathpenalty.org/innocence-isnt-enough-here-arizona-... [3] https://www.scotusblog.com/case-files/cases/shinn-v-ramirez/ https://www.scotusblog.com/case-files/cases/shinn-v-ramirez/

nonrandomstring 4y ago

"The Lie Behind the Lie Detector" had a big impact on me [1]. As a kid I made lie detectors (a 9 volt battery, 1M-Ohm resistor, BC108 transistor and buzzer) and got sent home from school for "Interrogating" the other kids. The teacher evidently thought it really worked - even though as an 8 year old I knew it was just an electronic trick. 40 years later the Iraqi government was purchasing thousands of ADE 651 "bomb detectors" [2] - basically a stick - that no doubt caused some poor dudes to get blown to bits by IEDs. All technology (indistinguishable from magic) has a cult-like aura around it, in that there's the reality of what it does, and a separate set of human beliefs about what it does. Cybersecurity is full of wishful and magical thinking in this regard. I sometimes feel like a kind of James Randi, trying to debunk the certainty people want and project on to technologies. [1] https://antipolygraph.org/lie-behind-the-lie-detector.pdf https://antipolygraph.org/lie-behind-the-lie-detector.pdf [2] https://www.cnet.com/culture/divining-rod-reborn-as-explosive-detection-device/ https://www.cnet.com/culture/divining-rod-reborn-as-explosiv...

ghastmaster 4y ago
Thank you. I had not heard of this product before. I want one. https://en.wikipedia.org/wiki/ADE_651 https://en.wikipedia.org/wiki/ADE_651 > According to Iraqi police officer Jasim Hussein, "The vast majority of the people we stop, it's because of their perfume". A fellow officer, Hasan Ouda, commented that "Most people now understand it's what gets them searched, so they don't use as much."
hatsunearu 4y ago
Ulgh, knowing the polygraph is a lie is actually a huge hazard for you. I once had to take a polygraph test, and I was freaking the fuck out because I knew being nervous will register me as a liar, and I wasn't actually lying at all. I tried my best to stay calm, but I was freaking out during the test, and I actually did fail the polygraph, but passed after a retest. It's such bullshit. I wish they got rid of this bullshit technology from this earth, because I had so much on the line and I was absolutely miserable before and during the test.
- ok_dad 4y ago

hammock 4y ago

how is blood spatter analysis bogus?

WheatMillington 4y ago

Fire forensics.

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