Based on English and (especially) Scottish primary and secondary sources it's really hard to agree with Mr Bejblik's sentence. Alhough some convincts were released by Scottish Privy Council to be enlisted into Gray's regiment, convicted murderers were not amongst them - as they were usually hand in Edinburgh, once sentenced to death Some beggars and vagabonds ('maisterless men haveand no laughfull trade no meanis of intertenyment') were also forcefully enlisted but hard to call them criminals. More than 100 Scots came from reiving clans from the Borders - I wouldn't jump to conclusion to call them criminals,. just because of their style of life. Sir Andrew Gray had his main recruitment camp in Scotland set in Monkigr, near Athelstaneford in East Lothian - and he was recruiting locally, with at least part of his soldiers coming from Catholic clans settles in area. One of such volunteers was John Hepburn, second son of th laird of Athelstaneford. All together 1400-1500 Scottish and 1000 English soldiers were recruited. Anonymous author of 'A Most True Relation of the late Procedeeings in Bohemia, Germany and Hungaria. Dated the 1. the 10. and 13 of July the present yeere 1620' wrote about Gray's regiment: 'Colonel Gray is (God be blessed) safely arrived in Lusatia with hos Brittans: he hath mustred two thousand foure hundred brave men; they are mightily praysed for their modest behaviour in their passage' - hardly something one can expect from regiment of criminals John Hepbrun with honour guard from Gray's regiment was send to Pragu to guard 'Winter King' - rather unusual for 'thieves and murderes', don't You think?
For those interested in Fynes Moryson's 'An itinerary...' it can be found online in English of course
but his works do not help us in regards to Gray's regiment, as it was published before outbreak of TYW.
In regards to Gray's regiment after 1620 - some officers were present at Bila Hora, as colonel later ransomed them. Rest of regiment, at the time of battle, was with Gray near Karlstejn. Gray was later defending Elbogen (Loket) and Falkenau (Sokolov) until surrender in April 1621, when remaining part of his regiment was allowed to leave to Frankenthal.