Explanation of a caution, courtesy of Exile to Whoville:
Investigations by the police
The formal caution
A mid-point between prosecuting and not pressing charges at all, is the
police discretion to issue a formal warning. Often, when police decide not
to prosecute, they will issue an informal warning to the defendant about
his/her future behaviour. Although begun initially for use in relation to
juveniles, it is now used quite frequently with adults as well.
What is a formal caution?
A caution is formal in the sense that records are kept of all cautions made.
However, they do not rank as previous convictions, although they may be
mentioned in court when being sentenced for a relevant subsequent offence.
For example, if having been cautioned for theft, you are subsequently
prosecuted and found guilty of a further theft, your earlier caution may be
mentioned during sentencing.
How long do they last?
There is no set time limit, but in practice they are kept for a minimum of
five years.
In order for a caution to be given in a case:
There must be enough evidence to prosecute
The defendant must admit the offence
The defendant (or the parents of a juvenile) must agree to the caution,
having been told that it may be mentioned in court in the case of future
offending.
The significant issue with a caution, therefore, is whether the person
concerned will accept guilt for the offence. A confession made in the
context of receiving a caution is not admissible as evidence in proceedings.
When are formal cautions appropriate?
They serve as a 'half-way house' in cases where it is not appropriate to
drop all charges completely, for example, because the offence is too
serious, but where also there are other considerations indicating that
prosecution may not be appropriate. This may be where the offender is a
juvenile who has offended for the first time, or where there are
'sympathetic considerations' relating to an adult, for example, the
defendant is very old or is showing signs of severe emotional distress.