syrakusos

Criminalistics: Science or Folkway?

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On May 8, 2012, I delivered four presentations to classes in forensics and psychology at Westwood High School in Round Rock, Texas.

Ahead of my May 8 talks to the forensics classes in the science department at Westwood High School in Round Rock, Texas, the teacher, Susan Seale, distributed a questionnaire of my own design.

Three intentions informed the instrument. I wanted to prepare the classes to think about the science of crime scene investigation. Second, how well could they correlate knowledge in general and about forensics especially. Also, I was fishing for an answer I did not have about the actual value of forensic psychology.

"Criminalistics: Science or Folkway?" on my blog here.

The problem is really their textbook. Like the one I used in a community college class in criminal investigations, theirs only presents ballistics, fiber, hair, etc., etc., as laboratory science without any discussion of the actual science (philosophy of science) behind them.

Only DNA testing meets the Daubert Test. While hair, fiber, shoe prints, etc., etc., may indeed be evidence, their value has never been scientifically validated. Fingerprints are the biggest lie in prosecutorial evidence.

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Fingerprints are the biggest lie in prosecutorial evidence.

I'm not sure what you mean by "lie" in this context. A lie is conscious attempt to hide a truth.

Maybe you mean "error"?

As for fingerprints, everyone's fingerprints are unique, so if via lab tests, a fingerprint can be identified as being from person X, it looks pretty scientific to me.

But maybe you mean by "lie" in prosecutorial evidence that the presence of fingerprints might be misinterpreted?

In domestic homicides for example, if a suspect's fingerprints are found on incriminating evidence, the defense often tries to attack the prosecution by claiming that naturally this person's fingerprints would be all over the home since he/she lived there.

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I'd like to hear this explanation also, Angela.

Michael, are you sticking with the word "lie," or, was that hyperbole...hell I am a professional at hyperbole...

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My review of Suspect identities by Simon Cole here.

http://necessaryfacts.blogspot.com/2011/01/fallibility-of-fingerprinting.html

As I point out on more recently here

http://necessaryfacts.blogspot.com/2012/05/junk-science-in-classroom.html

there is no statistically validated database of fingerprints, shoe prints, tire prints, hair, fiber, etc., etc.

I agree that I do not apply any scientific test to know my wife and I never confuse her with one of her cousins.

If you compare a complete set of ten clean prints, the individual differences can be spotted by anyone who can read the incredients on a can of soup. But, we have all had the experience of thinking we met someone we did not and conversely of not recognizing someone who knew us. So, too, with fingerprints, do we only see the matches sworn to in court. We never see the near misses, close comparisons, almosts, and maybes. There is no complete statistically validated published database of fingerprints. They keep it secret for a reason.

And when they match partials, the truth is out the door. How many "points" make a match? Scotland Yard insists on 16. Few American jurisdictions go to that extreme. Sometimes four "points" on a partial print of a single finger are enough for an "expert" to swear under oath in a court of law to a match.

DNA has odds. Fingerprints do not. DNA is science. Fingerprints are supposition.

I am not a certified examiner. I have been fingerprinted several times, of course. I brought a certified technician to a "Super Science Friday" presentation I did for middle schoolers at the University of Michigan. Nurses, for instance, are tough to fingerprint because they wash their hands so often.

Xray, when you say that a person's (latent) print from a scene matches their print on file, you are comparing apples to oranges. A complete set of ten clean prints inked on a card or scanned to a computer image are not the same thing as lifting and transferring a partial print left by sweat, blood, paint, etc.

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Xray, when you say that a person's (latent) print from a scene matches their print on file, you are comparing apples to oranges. A complete set of ten clean prints inked on a card or scanned to a computer image are not the same thing as lifting and transferring a partial print left by sweat, blood, paint, etc.

It may not be the same thing, but then it its always the totality of the evidence that has to be looked at.

So if a fingerprint (or palm print) where the required markers happen to match those of a suspect whom addtional evidence (like e. g. fibers), links to the scene of the crime, this can be quite incriminating.

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It may not be the same thing, but then it its always the totality of the evidence that has to be looked at.

So if a fingerprint (or palm print) where the required markers happen to match those of a suspect whom addtional evidence (like e. g. fibers), links to the scene of the crime, this can be quite incriminating.

I agree 100% that such "evidence" is compelling to a jury. This overwhelming junk science and pseudo-science and cargo cult science is why 20,000 to 50,000 innocent people are in prison in the USA right now. Of the 250+ people exonerated by DNA evidence, I believe that 70 or 75 actually confessed to the heinous crimes of rape or murder.

The police show you all this evidence - the fiber, the hair, the partial fingerprint - and they ask, "Who is the jury going to believe?" See the first video under "Don't Talk to the Police." 85% of cases are pleaded guilty. Why do you think that is? Take the plea and you are out sooner. Fight it in court and you are in prison longer.

Basically, most people are victimized by others close to them: friends and family, or co-workers. So, solution of the crime is not hard. In those cases, fingerprints, fiber, etc., are to convince the accused to confess. Often easily they are guilty. It is not a challenge.

In the other 15% of cases, the problems cascade. With 300 millions plus in the USA we have 3 million in prison, on probation, or on parole, nearly 1% of the population. Of those 3 millions, some "small" number, like 20,000 to 50,000 are factually innocent of the crime for which they have been imprisoned. When it is you who are one in a million, the numbers become meaningless.

The fact remains that hair, fiber, shoe prints, tire prints, and fingerprints are not science.

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I agree 100% that such "evidence" is compelling to a jury. This overwhelming junk science and pseudo-science and cargo cult science is why 20,000 to 50,000 innocent people are in prison in the USA right now.

But "innocent people in prison" does not automatically mean that 'false' circumstantial evidence has got them there. There is also false eyewitness testimony to consider, or cases of downright revenge where e. g. a scorned lover accuses her ex of rape..

And among the factually innocent also counted those who are - I'm not sure what the English term is - "imprisoned on remand"?

The fact remains that hair, fiber, shoe prints, tire prints, and fingerprints are not science.

I think this kind of evidence still does have a valid place in crime scene investigation,

And In today's time of DNA evidence, according to your theory, the number of innocents imprisoned ought to go down dramatically anyway.

But I sometimes think whether DNA evidence could also lead to falsely exonerating a guilty person.

"Unknown" DNA found on a victim for example (we all have lots of 'foreign' DNA on us I suppose). that was not left there by a perp, but which the defense then claims as exoneratng to their client.

But it always depends of course where this DNA is found. whether it is found in locations directly connected to a victim's death, or in less incriminatng locations.

I have studied (as a layperson) some criminal cases in great detail have been impressed by the acribic detail work and complex thinking that is required for the job of investigator.

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Weren't the Criminalistics a doo-wah singing group back in the 60s?

ba'al Chatzaf

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Ba'al, I was hoping for something more substantial, considering your lifelong work as a scientist.

... There is also false eyewitness testimony to consider, or cases of downright revenge ... And among the factually innocent also counted those who are - I'm not sure what the English term is - "imprisoned on remand"?

... And In today's time of DNA evidence, according to your theory, the number of innocents imprisoned ought to go down dramatically anyway.But I sometimes think whether DNA evidence could also lead to falsely exonerating a guilty person. ... impressed by the acribic detail work and complex thinking that is required for the job of investigator.

I do not have my class notes here, only the texts, but in a class in Miscarriages of Justice, I did bring up the one case of a man exonerated by DNA evidence who later was charged (and convicted) of a similar crime. It is not proof, but, like shoe prints and tire tracks is evidence, perhaps.

Also, DNA testing is called "fingerprinting" for a reason: it is not a complete match of a complete sample against a complete standard. (The largest human chromosome has 220 million base pairs (Wikipedia here) We have 46 chromosomes.). Rather, "genetic material" is chosen and replicated with PCR (polymerase chain reaction) and within the chosen sample, certain identifying "points" are sought. Other problems with DNA include chain of custody and the fact that this is very far removed from the experiences of most people.

In other words, take ballistics. We have enough exposure to machines from door hinges to automobile transmissions to understand that when a gun fires a bullet, it leaves marks from the magazine (or cylnder), firing pin, ejector, and rifiling. Moreover, beyond accepting that no two machine-made products are perfectly identlcal, we can accept that normal use will change the physical characteristics of any mechanism, rendering it different from others in its production run. So, when a technician (or "scientist") from a police laboratory says that examination under a microscope matches this bullet with this gun, that seems acceptable. Even though PCR is a high school biology kit, I have never run it. I certainly have not done it hundreds of times. When a technician (or "scientist") says that this sample matches that, how do I know?

Eyewitness testimony is hopelessly flawed. When we lived in villages of 300, sure, your statement that you saw Long Jack leaving the mill where Tom Miller was found dead is reliable. But the classic presentation What Jennifer Saw indicates that in a world of strangers, misidentification is far too easy and too common. That is another discussion and one that needs to be carried forward. Here, however, I would like to stay focused on the so-called "science" of criminalistics.

Investigators work hard, certainly the best ones do. Too often, they just take the easy route. The pay is the same, either way. In 85% of the cases police detectives just interview the people at the scene and let it go at that. The other cases provide the stories worth repeating.

I am working on a team of four technical writiers serving 40 project managers. They think they can write. We find them laughable. No one appreciates the hard work of a professional writer. What does "acribic" mean?

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