The Proviso
Even if the Court is persuaded by the points on appeal the Court may 'dismiss the appeal' if it considers that no substantial miscarriage of justice has actually occurred: s668E(1A). So for example, despite the fact that evidence has been admitted improperly or matters have been joined improperly on the indictment these errors are considered in relation to the strength of the case and if, after the court independently assesses all the evidence, it finds that the accused is proved guilty beyond reasonable doubt the appeal will fail (Weiss v The Queen (2005) 224 CLR 300.
UNLESS the errors are fundamental and negative a genuine trial (Wilde v R (1988) 164 CLR 365). If there are fundamental errors that go to the root of the trial and provide a 'significant denial of procedural fairness' (per Weiss v The Queen (2005) 224 CLR 300) the proviso does not apply, even if guilt can be established (e.g. Arulthilakan v R [2003] HCA 74; Cesan v The Queen [2008] HCA 52).
UNLESS the errors are fundamental and negative a genuine trial (Wilde v R (1988) 164 CLR 365). If there are fundamental errors that go to the root of the trial and provide a 'significant denial of procedural fairness' (per Weiss v The Queen (2005) 224 CLR 300) the proviso does not apply, even if guilt can be established (e.g. Arulthilakan v R [2003] HCA 74; Cesan v The Queen [2008] HCA 52).