RAINBOW &The King's Shilling, St Albans, 1842
I am sure that, in part, the "King's Shilling" is the key to what was going on. Army recruiting was carried out by men who moved round the country persuading young men to join the Army. The recruiter were paid commission for each recruit and persuasion usually took the form of getting the young men blind drink in a hostelry and when they recovered from their hang-over they discovered that they had accepted the King's shilling and had joined the army. You will find a detailed account of the activity at the time of the Napoleonic war on http://www.warof1812.ca/recruit.htm
For this reason I suspect that recruiting team of the 34th Regiment of Foot was only in St Albans for a few days, almost certainly staying in at an inn in the centre of town where they might meet suitable young men. They may well have female companions travelling with them - and it could even be that they sometimes used a pretty face to persuade the gullible young men that all the nice girls love a soldier.
It may well be that further information about the trial is held in the assize records at HALS, and I would like to have been able to look Jabez up in the published indexes for you - but unfortunately those for St Albans only go up to 1840 - so you will need to contact HALS. However Transported beyond the Sea lists very brief details to indicate that the incident happened at the Boot Public House. The Boot was (and still is) in the Market Place - the centre of the town, and undoubtedly a good recruiting area - and it is possible that the recruiting team were operating from this pub.
There is a web page for St Albans
and also one on The Inns & Public Houses of St Albans in the 19th Century
If you can add to the information given above tell me.