Quite a long post so probably best to break it down:
Researching my friend's Oxford family I have her 4th Great Grandfather as Thomas Johnson (possibly born abt 1789). He married Jane Green on 1st June 1803 in Charlbury. He was from the parish of Fawler.
How can he be born c.1789 if he married in 1803? That would make him 14 at marriage - which is very young indeed - and the marriage register does not say marriage by consent of parents, which indicates he was at least 21 when he married.
Thomas and Jane may have had more children in Black Bourton - yet to be researched - but possibly not if the record I have found for a Thomas Johnson being sentenced for transportation is correct.
A Thomas Johnson married a Jane Smith in 1822 in Black Bourton; I imagine these are the parents of the children who were baptised there from 1823 onwards.
In Charlbury, there were children baptised after John (1814):
Sarah (1816)
Mary (1818)
Mary Ann (1821)
My question is how can I find out more about the trial that took place in Oxfordshire on 27 June 1836.
https://www.ancestry.com/imageviewer/collections/1590/images/31251_A006052-00111?pId=857919
I want to find out if it is indeed my friend's 4GGF.
I have found a record that tallies on Convict Records
https://convictrecords.com.au/convicts/johnson/thomas/38540?fbclid=IwAR1S6E2_g_W7nMay_FIFhFi_qoVV0_b9_iuB7hJKojq83pzHo5dSoOoL4A4
The Thomas Johnson who was transported for 7 years was charged with "having obtained eleven pounds, under false pretences, from James Cook, of Burford."
With such a common surname as Johnson, I am a bit unsure why you feel this man is the same Thomas Johnson who was having children in Charlbury, especially when the age on the criminal register doesn't match up with Thomas' 1803 marriage.
Queenie