Thanks for the link, started a thread..Marian Beattie, 18, Aughnacloy, Co Tyrone, 31 March 1973
Article from 2013, including brief summary and original news footage:
1973 teenager murder case reopened
Podcast and summary of case:
BBC Radio Ulster - The Nolan Show - 'The Murder of Marian Beattie'
There's apparently no thread about Marian Beattie's case, but I wanted to highlight it in case anyone may be able to help, even after all this time.