WR
The short answer to your good question is that when the CPS was created, Parliament allowed the CAA (and some other bodies) to conduct their own prosecutions.
It means the investigator and prosecutor are the same body, which many regard as not being in the interests of justice.
chrisbl
They (CAA) still have to operate on the basis of a) is the prosecution in the public interest and b) the likelihood of securing a conviction.
In theory, that is correct and the CAA would claim that, in practice, those criteria are properly applied.
However, problems can arise where the body which investigates is the same body which decides whether to prosecute.
ie Where there is no independent/objective assessment.
eg Police investigate and gather evidence. The CPS (which is independent of the police) then decides if there should be a prosecution.
ie Whether the two criteria are met.
Many would say the problem is far greater where it is not only the same body but the same department which considers the first of those two criteria.
FL