The key police interview of a sexual assault complainant, who has since died, has been ruled inadmissible in court with a judge saying it appears to be because of "a failure of police training" in a "crucially important area".
An ACT Supreme Court trial starting on November 21 has heard that a man allegedly committed historical indecent acts on his adopted sister in 1971-75.
She then had major depressive disorder and received psychiatric treatment before she died by suicide earlier this year.
