Thought double jeopardy had been gotten rid of in England and Wales following Steven Lawrence?
Double jeapardy actually has a different meaning from the commonly assumed one, but can't be arse to go into it.
You can now be tried for an offence for which you were previously acquitted, it wasn't as a result of the Stephen Lawwrence murder, rather some woman whose name I can't remember.
off the top of my head the criteria to allow a further trial after acquittal are:
1. The offence needs to be serious, ie. homicide, rape or something else very naughty
2. New evidence is avialable now that would not have been avialable at the time (i.e. scientific advances etc) not just evidence that wasn't presented at the time of the first trial due to incompetence etc
3. the A-G's consent is obtained.
probably more in the criminal justice act 2003.