Children who do not understand the serious wrongness of their actions lack criminal capacity and cannot be convicted. At common law, children under seven are deemed to lack criminal capacity, children over 14 possess full capacity and children between seven and 14 are rebuttably presumed to lack capacity; the prosecution must prove capacity beyond reasonable doubt. Australia has increased the minimum age of criminal responsibility (MACR) to 10 and is considering a further increase. England & Wales and Northern Ireland have raised the MACR to 10 but have abolished the rebuttable presumption: at age 10, all children are assigned full criminal capacity. This article agrees with international calls for the MACR to be raised but argues that it is more important that the rebuttable presumption should be retained and extended. Children’s brains and decision-making capacities continue to develop throughout their teenage years at different rates. The rebuttable presumption provides individualised justice for children facing developmental difficulties. To wrongfully convict a child who lacks capacity will unjustly damage their life chances. Where a child does have capacity, a variety of evidence may be available to the prosecution to prove it. If the prosecution fails to discharge the burden, the child should be acquitted. The acquittal may be mistaken, but this error is far less harmful than a wrongful conviction.