Brian Clarke's Francis Bacon Trial series comprises two triptychs realised in stained glass and lead, The Obscene Mystery and Untitled Triptych, together with the autonomous stained glass work Between Extremities. Incorporating some of Clarke’s recurring motifs, including skulls and the fleur de lys, these works draw on his involvement in the Francis Bacon trials between 1998 and 2002. References to contemporary newspaper coverage of the case are integrated into the background of each work.

In his essay 'Brian Clarke: Traditions and Discontinuities' from The Journal of Stained Glass, vol. 29, Martin Harrison writes:

"The sombre triptych that memorialised Clarke’s ambivalence towards the Francis Bacon trials could be termed a modulator of darkness as much as light, since the majority of the picture field is occupied by sheet lead; against the negative black, the impact of the minimal colour passages is brilliantly intensified. The sole historical precedent for this system (and not one Clarke had in mind) is the extensive use of brown enamels favoured by certain Georgian glass-painters as a foil for dramatic chiaroscuro effects, but its renewal by Clarke is both a challenge to the imagination and a release of exciting potential."