Monday, May 28, 2007

Time Lines and Probabilities in German Courtrooms

In a controversial case in Germany a court of the first instance acquitted a man (Alfred B.) charged with committing a bank robbery. The evidence against the man included (forgive the following attempt at a translation of the article from Der Spiegel (May 21, 2007):
Alfred B. is arrested on the basis of statements made by the only two eyetwitnesses, and indications of guilt surface immediately: The police discover 14,970 Euros in the rear panel of an old refrigerator [at Alfred B.'s residence]. {Furthermore,] Alred B. had 10,000 Euros [in his possession] on the day of the crime, and a day later [a day after the day of the crime] he deposited 4,970 Euros in [a bank in a neighboring village]. Taken together, therefore, [Alfred B. had] almost as much as the approximately 33,500 Euros that were taken during the robbery. In addition, there were fourteen 500 Euro notes in the money found in Alfred B's possession. [At the behest of the perpetrator] the bank clerk put fifteen such notes in sacks during the robbery.
The two surviving eyewitnesses to the robbery identified Alfred B. as the perpetrator.

Furthermore, according to expert witnesses (the robber shot two people at the bank that he robbed), the perpetrator used a "Walther PP, caliber 7.65 cm." Alfred B. was the owner of precisely the same model revolver (which, however, he reported was stolen years earlier).

So why was Alfred B. acquitted?

One problem, it appears, was with the reported sequence of events (id.):

One of the principal witnesses, the farmer Bauer B., has an ironclad belief that he saw Alfred B. to the east of the scene of the crime at the time of th crime.
A higher-instance court reversed the lower court's acquittal and ordered a new trial.

What is the moral of this (unfinished) story?

The attorney for the family of one of the victims said this:

The big error in the [lower court's] opinion is that indications of guilt were hacked away [by the court] because doubts remained. But one must consider the larger picture: The probability that there was a doppelgaenger with such a gun, with similar rubber boots, and with almost exactly the same amount of money is close to zero."
  • My thanks to Prof. Lothar Philipps for alerting me to this case.
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