Hi, Jessie,
Don't worry about the codswallop !- I find this system a little bit confusing too - never sure what is a new message and what is the bit I'm trying to reply to!
Anyway, it had nothing to do with the seriousness of the crime - at that period, Perth was the General Prison for Scotland, and, once sentenced, people seemed to get shunted there from all over the country. I also had a (female) family member there in the 1860s, from Aberdeenshire - have also come across folk from the Borders, etc..
If you go on to this webpage for the Archives -
http://www.nas.gov.uk/onlineCatalogueType in William Thomson, and tick the box for 'Phrase', go down the date section and enter a fairly generous likely period, then hit Search.
If you don't tick Phrase, you'll get hundreds of pages with
William Smith and Robert
Thomson, etc., featuring !
I've just tried this from 1862 - 1882, and got 15 Persons and 86 Catalogue entries, none of which look correct on a quick look, but you could maybe spend more time on it?
If you get hold of a likely entry, hit on the Reference at the left-hand side, and it should come up with more details. A lot of the entries, by the way, are of Sequestration proceeedings ( bankrupcy) so not likely to be your man, I woldn't think.
If you do come up with a reference, and want to know more, let me know, and I'll check next time I'm in West Register House, where the legal archives are held. [Could be a couple of weeks or so, though, so hope you're not in a hurry.]
Janice