Another Forensics Competency Test; More Bad News

Friday, April 23rd, 2010

Researchers at the University of London used a suction device to create bruises on 11 subjects. They then took sequential photos of the bruises over nine days. They showed the photos to 15 forensic experts and asked them to order the photos chronologically. Forensic experts regularly testify about the age of bruises down to the hour, providing chronologies that allow prosecutors to give a suspect a window to have committed a crime. Or, alternately, to attempt to put a the crime at a time for which the defendant has an alibi.

But these particular 15 experts didn’t fare so well. The results:

Lead author, Margaret Pilling, an Honours Medical Student at Barts and the London School of Medicine and Dentistry, said: “The greatest accuracy, from forensic experts, occurred in very fresh bruises (between 0 and 12 hours) however there were still a number of significant misjudgements in this age range.

“The median difference between the estimated age and the real age was 26 hours – a considerable disparity. We conclude that forensic experts’ estimates of bruise age from photographs are, at best, unreliable.”

More on forensics aptitude here, here, and here.

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14 Responses to “Another Forensics Competency Test; More Bad News”

  1. #1 |  Michael Pack | 

    Forensics are a joke,I mean, you can be arrested for dui,minus a acccident or reckless driving.How,a little box says your a danger.They don’t want accurate tests or proof of harm or danger,just convictions.

  2. #2 |  Judi | 

    Radley, is there a reason the video on the link above showing West explaining the ‘bite mark’ and also the video in the article about Jimmie Duncan are no longer viewable?

    I’ve passed these links on to several people and the videos are no longer on the sites. It would be great if there was a way to put them online permanently.

    Seeing is often believing for a lot of people.

    Of course you know, I know and certainly believe. But there are a lot of folks who really want to see these.


  3. #3 |  Dave Krueger | 

    We conclude that forensic experts’ estimates of bruise age from photographs are, at best, unreliable.”

    Wow. I guess, at worst, they would be a way of throwing someone in prison based on fabricated evidence. Luckily, prosecutors and forensic “experts” are being aggressively disciplined for such abuses, making it a very risky proposition to continue such practices.

    Hahahahahaha! I’m the most full of shit person I know!

  4. #4 |  Nando | 

    Take that, CSI!

  5. #5 |  Andrew S. | 

    And Nando touches on the issue… jurors are… well, they’re idiots. If Horatio Caine can figure out time of death to the minute… and I mean he’s always right… then surely those real forensic investigators on the stand are always right too!

  6. #6 |  Galius | 

    They’re much more accurate when the experts are told ahead of time what time they’re supposed to have occurred.

  7. #7 |  Aresen | 

    Galius | April 23rd, 2010 at 11:47 am
    They’re much more accurate when the experts are told ahead of time what time they’re supposed to have occurred.

    And I play much better poker when I’m allowed to look at the other players’ hands.

    ‘Course, they get a mite techy when they find out about it.

  8. #8 |  pam | 

    I mean it’s always helpful when the forensic expert knows the prosecution’s theory. Forensics to fit.

  9. #9 |  Matthew | 

    CSI and the other forensic law enforcement shows all seem so hoaky to me. I think these shows may serve an alternative purpose besides providing crappy entertainment. Look how many of these shows are now shown each week, and how many of them run every day of the week. Sure, I think they are OK entertainment, especially when compared to reality TV. But, what is the underlying message they plant inside your subconscious? Forensics is real science? Forensics is always right, never making mistakes? Forensics evidence will always find the bad people? Who ever the forensics evidence identifies, they are the criminal, no exceptions, no mistakes.

    I think maybe the shows like CSI are created for the purpose of re-enforcing the idea that forensic science is exact and always correct. And only the very bad people are caught with forensics. Who ever the forensics evidence points to, they are the criminal. The general population is just soaking those messages up every night watching these shows.

    Think of how shows like this can manipulate a persons view of forensics. The common man sits down to watch the CSI show and it seems very plausible that the CSI technicians are doing very scientific looking stuff. And as the show progresses, the bad guy is found out because of the forensic work. The bad guy is caught and the world is a better place, roll credits. So later on, when that common man is asked to serve jury duty, I think there is an almost automatic acceptance of forensic evidence when it’s presented.

    I can sometimes spot the bull-crap science they constantly use in these shows. And how they try to pass it off as real. Sure, my friends argue that it’s just TV, and they can get away with it. But, you have to wonder how many people really believe some of this stuff. And how does that effect their perception of forensics over-all.

    With all these shows convincing people of the power of forensics and the use of it to find criminals, it makes it harder for people like Radly to convince them otherwise.

  10. #10 |  Dr. T | 

    I’m a pathologist who had a smidgeon of forensics training. The medical examiners I knew would never make ridiculous claims that they could look at a bruise and know its age within a few hours. There are too many variables: the depth of the bruise, the extent of blood vessel rupturing, the blood pressure of the victim, whether the victim was in shock (less blood flow to skin and slower progression of the bruise), whether the victim was ambulatory, whether the victim was taking aspirin or anticoagulants or steroids, etc.

    There are numerous really good forensic pathologists in the US. Unfortunately, there are also many people who claim knowledge of forensics that they do not possess. We need to weed out the fakers and the frauds.

  11. #11 |  Mark Z. | 

    Dr. Ed Friedlander, certified pathologist, on the timing of bruises:

    Colors of a bruise: Blue/purple -> violet -> green -> yellow -> vanishes. Sadly, the rate of color change is tremendously variable, and you can’t use it to estimate the time of a bruise. One recent study (For. Sci. Int. 50(2):227, 1991) found that the only reliable rule is that yellow always means >18 hours. Uh, one of my skydiving bruises showed yellow at 16 1/2 hours.

    Pretty reliable: If the color has clearly not begun to change, it is less than 48 hours. If the color has obviously changed and become variegated, it is more than 48 hours.

    Unless there is a hematoma that will organize, histology will usually only show the presence or absence of hemosiderin in the bleed. … Hemosiderin, usually not present until 72 hours, may sometimes be present by 24 hours.

    (Note: Hemosiderin is leftover iron trapped in the tissue as blood cells break down, and can be seen very clearly with chemical stains. This would have to be done on autopsy.)

  12. #12 |  Stephen | 

    Here is some more stuff on forensic science of the arson variety in TX.

  13. #13 |  armyvet_lawstudent | 

    Thank you for continuing to spread the word about the mounting evidence of forensic smoke-and-mirrors techniques that are used to dazzle juries every day.

    There’s a widely-recognized phenomenon in criminal jury trials called the “CSI Effect.” With the advent of these shows in which the evidence is always reliable and all well-trained analysts conduct industry-accepted scientific testing to the procedural letter, juries are now trained to afford ALL forensic evidence more weight than it often deserves.

    I wish more judges would get on board and require a higher standard for “expert” testimony, rigorously apply Daubert and make the party offering the witness prove that these experts fall in line with the rest of the scientific community. We would never have heard of Michael West if he was never permitted to bring his untested, unrecognized, blue-light special bullshit into the courtroom.

  14. #14 |  Corkscrew | 

    Wonder why they used the median difference rather than mean? Obvious explanation: there are a few exceptionally bad judgements that were skewing the figures. It would be interesting to know where those outliers came from…