NEW laws which came into force towards the end of 2011 did not remove double jeopardy – where someone cannot be tried more than once for the same crime – but instead created a number of exemptions.
One key exemption is where compelling new evidence emerges, such as DNA or a new witness, which substantially strengthens the case against an accused.
However, prosecutors admit it is harder to justify bringing a case under the 2011 act than it would be to bring one normally.
That means the test a judge would apply to the quality of the new evidence against the accused will be tougher than the test the prosecution service itself applies to a case passed to it by the police, before deciding whether to take it to court.
It is, therefore, unlikely that dozens of cases based on the new law will arrive back in court, but a small handful of the most serious are likely to be reopened.
Other exemptions include where an original trial was tainted, such as through intimidation of a jury member.
Prosecutors could also apply for a new trial if evidence comes to light that the acquitted person has later admitted the offence.
And a person could also be prosecuted again, on a more serious charge, if the victim dies.
For instance, if someone is convicted of a serious assault while the victim is in a coma, they could yet face a murder charge if that person subsequently dies of their injuries.