Despite being under the cosh for the opening 20 minutes, the Saints held firm to bounce back and lead at the interval following fine goals by Stuart André and Craig Leitch.
Dave Watson hit Trinity’s crossbar shortly after the break only for Trinity, who had defender Scott Jones sent off following two cautions in the 80th minute, to force extra time following scores by Allan Brown and Stephen Wilkinson.
Both teams had chances to have won inside 90 minutes, Trinity failing to get on the end of some good crosses while St Paul’s substitute Jean-Paul Martyn was denied at the death by a fine save from Jimmy Styles.
Jamie Allan restored St Paul’s lead from close range in extra-time before Leitch scored the second of a deserved hat-trick – his fourth treble of the season – from a free kick.
Composed substitute Darren Swanson stroked home Trinity’s third only for the Saints to go 5-3 ahead with Leitch completing his treble with a crisp finish off a crossbar for this 24th goal of the season.
Trinity were not finished and Dave Lloyd pulled back a late consolation from a header.
St Paul’s play the winners of tomorrow night’s semi-final between Grouville and Sporting Academics at Springfield on Tuesday 12 April.
St Paul’s: Daniel Evans; Shaun Irving, Lee Bradshaw, James Fortune, Jamie Allan; Glen Durrans, David Watson, Stuart André, Stephen Jones, Lucas Parker; Craig Leitch.
Subs used: Jean-Paul Martyn, Danny Hughes, Karl Hayes.
Cautioned: Parker.
Trinity: Jimmy Styles; Allan Brown, David Lloyd, Chris Richards, Scott Jones; Dave Le Roux, Lee Jones, Stephen Wilkinson, John Beatson, John Fitzmaurice; Jimmy Reilly.
Subs used: Darren Swanson, James Hayward.
Sent off: Scott Jones.
Cautioned: Lloyd, Lee Jones.
Officials: Andy Norman, Andy Cox, Ian Solomon.
