This article considers two issues in relation to the criminal transmission of HIV. Currently the use of condoms, and a defendant’s viral load, has not been an issue that has been raised in the courts. The article considers how the defence, prosecution and judge may deal with such evidential issues. It will discuss how an expert opinion may be utilised or discredited by counsel for the defendant and counsel for the prosecution. The article will consider how the defence can demonstrate that the defendant was not reckless and how the prosecution can establish that the defendant was actually reckless. It was also assess how the judge, in trial, may address condom use and the level of the defendant’s viral load when directing the jury. Finally it is argued that it is in the public interest to allow condom use and viral loads to be used to negate recklessness.