On 17 August 2012, a Swissair A320 being positioned under radar vectors for arrival at Geneva was inadvertently vectored into conflict with a Cessna Citation already established on the ILS LOC for runway 23 at Geneva. Controller training was in progress and the Instructor had just taken control because of concerns at the actions of the Trainee. An error by the Instructor was recognised and de-confliction instructions were given but a co-ordinated TCAS RA still subsequently occurred. STCA was activated but constraints on access to both visual and aural modes of the system served to diminish its value.