I thought I had all of Niamh Parsons' recordings, but this song is on a CD I haven't seen, The Old Simplicity. This page (click) says "Blue Murder" is by Scots/New Zealand songwriter Alistair Hulett, on asbestos mining conditions in Australia.
I really enjoyed her performance when she was here in 2004. She said she lurks at Mudcat occasionally - maybe she'll drop in with an answer.
-Joe-