Friday, March 27, 2009

Postscript to the Story of the DNA Pixie Dust in the Phantom of Heilbronn Case

A representative of the state prosecutor's office in Heilbronn officially confirmed that the source of the DNA found at about 40 crime scenes in Europe was not the hypothesized persistent peripatetic perpetrator called the "Phantom of Heilbronn" but, rather, a mercifully-unnamed female employee at an unnamed packing company somewhere in Bavaria. (The female employee presumably did not bother to wear gloves when packing the cotton swabs.) See "'Phantom-Mörderin' ist ein Phantom [The Phantom Murderer is a Phantom]," Spiegel Online (March 27, 2009).

The "Gold Standard" Bites the Dust! (gratuitous editorial comment by PT)

So: Did someone win the 300,000 Euro award for providing definitive clues to the (non-)identity of the Phantom of Heilbronn? If not, why not?

the dynamic evidence page

Thursday, March 26, 2009

DNA as Pixie Dust

For many months police in Germany and other parts of Europe have been searching for the "phantom of Heilbronn." See my earlier post, A Malicious Fairy Princess Spreading Spreading Pixie Dust Laced with DNA over European Crime Scenes? (May 14, 2008). This "woman without a face," DNA tests showed, had committed six different murders and also other crimes in various towns in Germany and Europe. A reward of 300,000 Euros was offered for clues to the identity of this female miscreant.

Oops. Yes, the crimes were committed. But the thesis that one evil woman committed all of them was, it turns out, very, very probably false. See "Eine sehr peinliche Geschichte," Spiegel Online (March 26, 2009).

What led to this snafu?


More precisely, unsanitary packing procedures during the manufacturing process, perhaps.

The Spiegel story (in very rough translation) tells us:
It now appears that the chances of finding the trail of the mysterious suspect are slimmer than ever before -- because she apparently doesn't exist. According state's attorney Heilbronn, the Baden-Wuerttenberg Office of Criminal Affairs is now investigating whether the cotton swabs ["Q-tips"] that investigators used to collect DNA samples [at crime scenes] had already been contaminated with DNA and had thus led investigators on a false trail.

According to a report in, the matter involves a packager [a packer, an employee] who worked for the manufacturer of the swabs that were used [at the crime scenes]. According to this report, the swabs were, to be sure, sterilized. But, according to Christian Rueff of the University of Zurich, such sterilization of the swabs does not affect contamination of the swabs with DNA by cells of the human body. [PT: The employee, I presume, held the cotton swabs in her hands when putting them into boxes or other containers.] The manufacturer delivered cotton swabs to various places in Germany and and also in France and Austria.
The article then proceeds to describe what led some observers to believe that the phantom woman might not in fact exist. One general problem was the large number of crimes -- 40 -- that the "phantom" supposedly committed in, supposedly, widely dispersed locations in Europe. Another hint that something might be amiss was that the supposed perpetrator supposedly began committing the crimes in 1993. But the immediate reason for doubt that a single woman committed the 40 or so crimes was the discovery that swabs of documents owned by a person who died in a fire had DNA that matched the DNA of the "phantom" -- which, an official proclaimed, "really could not be."

An official at the state prosecutor's office stated it was even possible that the cotton in the cotton swabs used in the police investigations was contaminated with DNA when it was plucked from the plant.


My thanks to Lothar Philipps for alerting me to this story.


Clarification: The corpse found in the fire apparently was never thought to be the corpse of the suspected culprit. The testing of the documents the dead person had owned aroused suspicion because the second time the documents were tested no matching DNA was found. See "'DNA bungle' haunts German police," BBC News (March 26, 2009).

the dynamic evidence page

Wednesday, March 25, 2009

Folk physics, common sense, inference, and intelligence

Perhaps epistemology (a general theory of human knowledge) must ride on the back of ontology (a theory of what is and how things-that-are work).

Perhaps metaphysics = sophisticated folk physics.

Folk physics should make use of the insights of physics -- and much else (e.g., neuroscience).

But folk physics -- metaphysics -- should not allow itself to be displaced by, e.g., physics or neuroscience.

Do not think that matters such as common sense and folk physics are unintelligent. They harbor much intelligence. If a special science can explain them, it will prove that it too is very intelligent. (But no special science can yet explain common sense, or "ordinary" intelligence.)

Of course, physics, neuroscience, etc., have much intelligence that ordinary intelligence lacks. But this fact does not render folk physics, common sense, etc., unintelligent.


the dynamic evidence page

coming soon: the law of evidence on Spindle Law

Hájek: Whether You Like It or Know It or Not, You Have a Reference Class Problem

Alan Hájek is an extraordinarily perceptive commentator on (the) reference class problem(s). See "The Reference Class Problem is Your Problem Too", Synthese 156: 185-215. 2007. He maintains that conditional probability should be a "primitive" for axiomatization of probability theory and that taking this view dissolves the "metaphysical" form of (the) reference class problem(s). However, he candidly admits this approach does not dissolve the epistemological version of the problem(s) [footnotes omitted]:
Now, the bad news. Giving primacy to conditional probabilities does not so much rid us the epistemological reference class problem as give us another way of stating it. Which of the many conditional probabilities should guide us, should underpin our inductive reasonings and decisions? Our friend John Smith is still pondering his prospects of living at least eleven more years as he contemplates buying life insurance. It will not help him much to tell him of the many conditional probabilities that apply to him, each relativized to a different reference class: “conditional on your being an Englishman, your probability of living to 60 is x; conditional on your being consumptive, it is y; …”. (By analogy, when John Smith is pondering how far away is London, it will not help him much to tell him of the many distances that there are, each relative to a different reference frame.) If probability is to serve as a guide to life, it should in principle be possible to designate one of these conditional probabilities as the right one. To be sure, we could single out one conditional probability among them, and insist that that is the one that should guide him. But that is tantamount to singling out one reference class of the many to which he belongs, and claiming that we have solved the original reference class problem. Life, unfortunately, is not that easy—and neither is our guide to life.

Still, it’s better to have one problem than two. I will leave it to others to judge the extent to which I have succeeded in ridding us of the metaphysical reference class problem. But I am aware that I have not solved the epistemological problem. I invite you to join me in the search for a solution for the interpretations of probability that have a genuine claim to being guides to life. After all, whichever interpretation you favor, the epistemological version of the reference class problem is your problem too.

  • One man's metaphysics is another man's physics?
    Folk physics?
    Folk physics has its uses -- and in an important sense it may be even "true."
  • P.S. I suspect that a successful "solution" to the epistemological version of the reference class problem(s) requires a bit of metaphysics (i.e., some basic assumptions about [wo]man and the world [s]he inhabits).
    N.B. By putting solution in quotation marks I do not mean to assert that a satisfactory solution of some kind is impossible. (Of course, there are solutions and there are solutions: one solution will not necessarily solve -- thank goodness! -- every possible problem about the choice and use of reference classes.)

    the dynamic evidence page

    coming soon: the law of evidence on Spindle Law

    Tuesday, March 24, 2009

    A Practical Solution to the Reference Class Problem?

    Professor Edward K. Cheng argues for A Practical Solution to the Reference Class Problem, forthcoming 109 Columbia Law Review (2009). The paper's abstract states:
    The "reference class problem" is a serious challenge to the use of statistical evidence that arguably arises every day in wide variety of cases, including toxic torts, property valuation, and even drug smuggling. At its core, it observes that statistical inferences depend critically on how people, events, or things are classified. As there is (purportedly) no principle for privileging certain categories over others, statistics become manipulable, undermining the very objectivity and certainty that make statistical evidence valuable and attractive to legal actors. In this paper, I propose a practical solution to the reference class problem by drawing on model selection theory in statistics. The solution has potentially wide-ranging and significant implications for statistics in the law. Not only does it remove another barrier to the use of statistics in legal decisionmaking, but it also suggests a concrete framework by which litigants can present, evaluate, and contest statistical evidence.

    the dynamic evidence page

    coming soon: the law of evidence on Spindle Law