A High Court jury has watched a video of George Gwaze's first police interview before the death of his niece in Christchurch Hospital.
Mr Gwaze, 60, is on trial for the murder and sexual assault of Charlene Mazaka in Christchurch in January 2007.
The Crown says the 10-year-old died after a forceful sexual attack by the accused, but the defence says she died of toxic shock arising from her HIV.
On Tuesday, the Christchurch court heard evidence about small tears in the girl's rectum the defence attributes to the severe diarrhoea caused by her advanced HIV infection.
When asked by Detective Paul Johannsen how he thought the girl sustained that damage, Mr Gwaze replied that he had no idea.
Mr Johannsen said in the interview that there was evidence of sexual violation and the girl was effectively brain dead due to a lack of oxygen.
He told Mr Gwaze that what was done to Charlene would have caused excruciating pain and repeatedly asked the accused if he had anything to do with it.
Mr Gwaze told the officer he nothing to do with the child's injury.
Earlier, the court was told the amount of semen belonging to George Gwaze found in Charlene Mazaka's underwear equated to less than 1/100,000th of a grain of sugar.
The defence says minute traces of sperm found on the girl's bedding and clothes could have been transferred through general household laundering.
Under cross-examination from defence lawyer Jonathan Eaton, ESR scientist Susan Vintiner said a grain of sugar weighs 200 million picograms and semen found in the girl's underwear equated to just 2500 picograms.