Probability:The Prosecutor's Fallacy.?

Question

Question:An accused prisoner is on trial.The defence lawyer asserts that,in the absence of further evidence,the probability that the prisoner is guilty is '1' in a million.The prosecuting lawer produces a further piece of evidence and asserts that,if the prisoner were guility,the probability that this evidence would be obtained is '999' in '1000',and if he were not guilty it would be only'1' in '1000';in other words,P(evidence/guilty)=0.999,and ...

..P(evidence/not guilty)=).001.Assuming that the court admits the legality of the evidence,and that both lawers's figures are correct,what is the probability that the prisoner is guilty? Comment on your answer.

Answer 1

I think that you add the two sets of odds together.  So therefore I think the odds that the prisoner is guilty are 999,001/1,000,000.

1/1,000,000 plus the extra probability due to the new evidence, 999,000/1,000,000.  I think the two are cumulative.

Not sure how else to comment.