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**0123** Hello. I am having problems with this prob question, thanks for your help:

G= guilty

P(G)= 2/3

I= innocent

P(I)= 1/3

The judge comes to know the result x of the test of DNA of the accused person. If guilty, the probability of x is 90%. If innocent is 5%.

Which condition on the probability of x, subject to the two events G and I has to be satisfied so that the final probability atributed by the judge to the innocence I is 100%.

the book says P(x|G)=0. Why? I can't get it. Thank you very much.