Hi Linda

The real expert in Oxfordshire criminal records is a good friend of mine called Carol Richmond.  She has published many excellent books based on extensive research in all sorts of sources.  You'll find them for sale at Oxfordshire Record Office or via the OFHS website at www.ofhs.org.uk/books.html under the heading Oxfordshire Black Sheep Publications.  (Before I go on to tell you how wonderful they are, I should point out that officially I am part of that publishing concern, but only on paper: Carol does all the work and takes all the proceeds!  So this isn't a plug for my own company!).

In the 6-part series of her books called "Banished! Sentences of Transportation from Oxfordshire Courts 1787-1867" Carol gives details of all the people she could find who were sentenced to transportation from Oxfordshire courts.  They're arranged alphabetically.  I happen to have the volume covering surnames O to S: the only Olivers in it are Solomon & Joshua, sentenced to transportation to Bermuda for stealing turkeys.

Then there are Carol's transcripts of calendars of prisoners tried at the Assizes or Quarter Sessions courts in Oxford, which she has split into three chronological volumes, altogether covering 1831 to 1842. 

My favourites are, I think, her "Oxford Gaol Prisoner Portraits" series, based on a fantastic photograph album at Kew.  This is where the photo of Stephen Oliver comes from which is I think in the "Facts & Happenings" section of this site.  The mug shots are mainly from the 1870s, though, so later than the period you're asking about.

I have a vague recollection of there being an index of deaths in Oxford prison (I think I've seen it at Oxfordshire Studies, among the parish register transcripts).  You can probably buy that from OFHS too.

For coverage of crimes and trials outside Oxfordshire, try looking at the "Criminal Registers" now searchable on Ancestry.  They don't give much information about cases but might point you to a date and place of trial.  Then you will need the "bible" on this subject, David Hawkings' "Criminal Ancestors" (second edition came out quite recently, 2008 maybe?) to guide you through which records are where.  Another thing that's now on Ancestry is a collection of lists of convicts on ships bound for Australia. (There's one for the First Fleet, one for the Second Fleet, and one for all the others.) 

If any of them went to Tasmania (like my naughty ancestor William Carter of Sunderland), you are in luck, as the Tasmanian Archives have digitised a lot of their criminal records.

That should keep you busy for a while!  Good luck with the searching...

Jane