A former high-ranking Health and Welfare Ministry official repeated a not guilty plea Friday to the charge of professional negligence in an HIV infection scandal involving the deaths of more than 500 hemophiliacs as his lawyers made final arguments in the Tokyo District Court.

The defense counsel claimed Akihito Matsumura, 59, accused of being responsible for the deaths of two people by failing to implement measures to halt the use of HIV-contaminated blood products in the 1980s, is completely innocent as the mechanisms of AIDS and HIV infection were not fully understood at the time.

"The prosecutors are supporting their allegation by looking back in hindsight with their current knowledge, thus their claim is unjust," one of the lawyers said. "If the facts are acknowledged by distinguishing the technology and knowledge of the time, the innocence of the accused will be clarified."