We can start with by looking to s 141 of the Evidence Act 1995 (Cth) where the criminal standard of proof is as follows:

(1) In a criminal proceeding, the court is not to find the case of the prosecution proved unless it is satisfied that it has been proved beyond reasonable doubt.

(2) In a criminal proceeding, the court is to find the case of a defendant proved if it is satisfied that the case has been proved on the balance of probabilities.

At its most basic level, beyond reasonable doubt means to be certain, as Barwick CJ observed in Keely v Brooking (1979) 143 CLR 162; 25 ALR (at 169; 48):

“Adherence to the well understood standard of proof in the trial of criminal offences is quite adequate to protect the individual charged summarily with contempt of court. To be satisfied beyond all reasonable doubt is, for the purposes of the law, to be certain.”

In R v Standley (1996) 90 A Crim R 67 (SA CCA), the court  after directing on proof beyond reasonable doubt stated the following, “[I]f you think there is a reasonable possibility that the accused is not guilty, then he’s entitled to be found not guilty”.

The notion of innocent until proven guilty, and guilty beyond a reasonable doubt are dearly held precepts within Australian criminal law and should not be taken lightly.