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"I teach the Bayesian approach to post-graduate students attending my 'Applied Bayesian Statistics' course at Cambridge, and so I must now tell them that the en

"I teach the Bayesian approach to post-graduate students attending my 'Applied Bayesian Statistics' course at Cambridge, and so I must now tell them that the entire philosophy behind their course has been declared illegal in the Court of Appeal. I hope they don't mind." Classic. I was told (at same uni) that, in a case involving DNA evidence, I could ask to be dismissed from a Jury, citing training in Bayesian statistics (which was prohibited because reversing the scientific certainty to look at false positives, in cases with weak circumstantial evidence, essentially kills DNA evidence's usefulness. If someone was in the right city, you expect hundreds of DNA matches out of millions of people, but if you can track them to the right street at the right time, you would expect 0.001 matches, and thus the evidence points to them much more strongly.)

jacques_chester 14y ago
Everything you hear about law that was not conveyed to you by a lawyer, a law lecturer or a judge is probably horseshit. People love to think they know some obscure wrinkle, some cool loophole, some nifty curio about the law. But so many of the stories you hear are just stories. ps. a better way to get disqualified is to have studied law.
- tehwalrus 14y ago
  indeed, this was my point. I didn't even contemplate trying it when I was called for jury duty.
Anderkent 14y ago
essentially kills DNA evidence's usefulness Could you elaborate? What kind of (valid) use does DNA evidence has that is disproved by bayesian reasoning?
- gizmo 14y ago
  Example DNA useful: Cops find criminal's blood at crime scene. Cops track down murder suspect using security video. Find suspect. Take DNA sample. Sample matches DNA at crime scene. DNA proves guilt beyond reasonable doubt 1:1000000. Example DNA not useful: Cops find suspect's blood at crime scene. Cops peek in DNA database and find 3 people in the region with matching DNA. One of them sort of looks like the shadow in the security video. They arrest him, get him picked out of a lineup and say DNA matches blood at the crime scene in the trial. Cops say DNA evidence proves guilt with odds 1:1000000, but odds of innocence are the complete opposite and closer to, say, 1000:1.
  - Anderkent 14y ago
    Right. I didn't realize DNA was used to locate the suspect, thanks.
    - tehwalrus 14y ago
      gizmo says what I meant, indeed. In the UK, the police have been keeping a DNA database of everyone ever arrested for anything; they run samples through it from crime scenes. The ECHR has (I think) ruled that this is illegal, because of this sort of error, but the Home Office refuses to listen to European Courts, or indeed mathematics, when it comes to crime.
rayiner 14y ago
The quote is stupid. Nobody declared anything illegal. They put boundaries on what evidence can be presented to juries, which is a key function of judges. In the American rules of evidence, evidence is only admissible if its probative value outweighs its prejudicial effect. That's why, for example, judges ban information, generally, of past crimes. While criminals tend to be more likely to commit another crime, the jury gives such evidence weight beyond its actual value. The same can be true of expert statistical testimony.

jacques_chester 14y ago

Everything you hear about law that was not conveyed to you by a lawyer, a law lecturer or a judge is probably horseshit. People love to think they know some obscure wrinkle, some cool loophole, some nifty curio about the law. But so many of the stories you hear are just stories. ps. a better way to get disqualified is to have studied law.

tehwalrus 14y ago
indeed, this was my point. I didn't even contemplate trying it when I was called for jury duty.

Anderkent 14y ago

essentially kills DNA evidence's usefulness Could you elaborate? What kind of (valid) use does DNA evidence has that is disproved by bayesian reasoning?

gizmo 14y ago
Example DNA useful: Cops find criminal's blood at crime scene. Cops track down murder suspect using security video. Find suspect. Take DNA sample. Sample matches DNA at crime scene. DNA proves guilt beyond reasonable doubt 1:1000000. Example DNA not useful: Cops find suspect's blood at crime scene. Cops peek in DNA database and find 3 people in the region with matching DNA. One of them sort of looks like the shadow in the security video. They arrest him, get him picked out of a lineup and say DNA matches blood at the crime scene in the trial. Cops say DNA evidence proves guilt with odds 1:1000000, but odds of innocence are the complete opposite and closer to, say, 1000:1.
- Anderkent 14y ago
  Right. I didn't realize DNA was used to locate the suspect, thanks.
  - tehwalrus 14y ago
    gizmo says what I meant, indeed. In the UK, the police have been keeping a DNA database of everyone ever arrested for anything; they run samples through it from crime scenes. The ECHR has (I think) ruled that this is illegal, because of this sort of error, but the Home Office refuses to listen to European Courts, or indeed mathematics, when it comes to crime.

rayiner 14y ago

The quote is stupid. Nobody declared anything illegal. They put boundaries on what evidence can be presented to juries, which is a key function of judges. In the American rules of evidence, evidence is only admissible if its probative value outweighs its prejudicial effect. That's why, for example, judges ban information, generally, of past crimes. While criminals tend to be more likely to commit another crime, the jury gives such evidence weight beyond its actual value. The same can be true of expert statistical testimony.