This CCTV, posted to YouTube by BroadSheet.ie, shows the locals' confusion as a pint of Smithwick's explodes. The pint, as you can see, is unattended and undisturbed on the table.
Of course the breakage, it can be reasoned, was caused by the fact that glass was very hot coming out of the dishwasher before the very cold beer was poured into the glass causing the glass to contract and break.
However, we prefer the owner of Barney Mac’s explanation that the pub is haunted by the ghost of former patron Joe Murphy. Apparently Murphy was a Beamish stout man. Maybe he took offense to Smithwick's being drunk.