UK court rules against use of Bayes' Theorem

[katipunero]

All court cases are decided based on probability. There is no rule as to what probability determines resonable doubt, but every judge and/or juror makes the decision on their own based on what they believe it means and what is acceptable to the individual. On the other hand with civil cases, it simply comes downto which side has the greater probability.

i think we're not using the word probability in the same sense as the OP and the article did.

you equate belief, presumption, reason, common human experience, finite possibilities of human activity and acceptable inferences with probability.

probability, as i use it, means weighted values, odds, chances and statistics. so when i say probability of guilt is the wrong way to convict a person, i use it in the sense that a judge or juror should not convict even if he thinks that his decision may be 9 out of 10 times correct.

as someone pointed out, using probability of guilt in that sense could mean a person who wins the lottery might be successfully tried and convicted for swindling since the chances of winning the lottery without rigging the system or altering the ticket is incredibly low.

this fallacy, a dangerous misuse of probability to secure a conviction, is still being used today, although mostly inadvertently or out of ignorance. the fact is, it makes it so that the accused now has the burden to prove his innocence in court!

 

[say1988]

Because you consider all factors combined.
Yes the probability of winning a lottery without rigging the system is low.
But what is the probability that this individual is capable of rigging the lottery (both morally and technically)?
What proportion of lottery winners rig the system?
Is there any evidence that something untoward actually occurred?

I would bet that the case in question here there was plenty of evidence considered other than this Bayes theorem. While that one piece may have been essentail to the conviction, it alone probably wouldn't have been enough.

Individuals deciding don't do actual statistical analysis, but in their head they determine the probability that a) a crime was committed and b) that the defendent committed said crime. Then they compare this to their idea of "reasonable doubt" to decide whether or not they can vote to convict. Since virtually nothing is a certainty it comes down to a probability judgment.

 

[GoodGame]

 

[azzaman333]

why the hang up on probability? if you're "not talking about single pieces of evidences proving anyone did a crime" then what's this talk on probability about?

the point of the article was that it was wrong for the judge to excluded the theorem as circumstantial evidence all because he did not believe or was not convinced that it was enough to show the probable guilt of the accused---can you see what's wrong there?

My initial point was that the end result of every trial is a conclusion is made based upon the probability that the person committed the crime, and that that probability is calculated in the mind of the judge/jury based upon all available evidence.

The article merely describes how poorly people understand statistics, judges included.