Manager Tommy Wright had made it clear before the game that he wanted two wins from their final two matches to make sure of qualification to the knockout phase of the cup, and he got the perfect start in an even tie.
Falkirk were competitive, but never really threatened the Saints goal and Scougall’s well-worked first-half goal proved enough for Wright’s side to claim three points that take them two points clear of Montrose.
There was little to excite the crowd in the opening quarter of the match at McDiarmid Park, with neither side threatening in the final third.
David Wotherspoon had the first real shot in anger, curling over from outside the area following a rehearsed corner routine, but Wright did not have to wait too much longer before the deadlock was broken.
Thirty minutes were on the clock as Richard Foster played a neat reverse ball to cut the Bairns defence in half and find Scougall, who had made a well-timed run and finished smartly into the corner.
It was a rare moment of quality in a game that was dominated by niggly fouls and regular breaks in play, but Saints were deservedly ahead going into the break.
The visitors came out with more intent in the second half but wasted a shot on goal as Tom Owen Evans sliced over, before St Johnstone hit back as Tony Watt, pictured, and Murray Davidson were denied from close range.
The visitors almost grabbed a dramatic equaliser with the last kick of the game but following a frantic goalmouth scramble, Scott Harrison saw his shot well saved by goalkeeper Zander Clark as Saints held on to claim the win that all but sends Falkirk out of the competition.