Faith in the justice system is derived from it being been to be fair and even-handed. It is not merely faith on the part of victims that offenders will be found guilty, but faith on the part of innocent defendant that they will be found innocent.  The double jeopardy rule reinforces faith in the justice system because it forces the prosecution service to make the best possible case that they can – because they only get one shot to make it. It also means that defendants can feel secure in submitting themselves to trial on the basis that an acquittal represents complete security from future accusations.  Abolishing the double jeopardy rule would actually undermine confidence in the system – overturning an acquittal is an explicit statement that the system produces false negatives. If it becomes widely accepted that a not-guilty verdict is meaningless then the principle of the presumption of innocence loses its force.