Murray Davidson had given Saints an early lead before on loan defender Louis Laing was dismissed on 25 minutes.
Sutton blasted his shot into the top corner of the net from just inside the box after Dominic Thomas had weaved past three Saints defenders to create the opportunity.
Motherwell had been opened up with ease after just nine minutes when Chris Kane slipped a pass into the penalty area and Davidson kept his composure to slot the ball beyond the advancing Dan Twardzik.
The visitors almost doubled their advantage as Tam Scobbie evaded his marker to prod the ball wide of the far post from a Simon Lappin corner.
Having survived that scare the situation deteriorated for Motherwell on 25 minutes as Laing collided with Kane just outside the penalty area and was dismissed by referee Willie Collum.
From the resulting free-kick David Wotherspoon curled the ball wide of the Twardzik’s right post.
Three minutes before the break Davidson burst into the Motherwell box but his strike was tipped behind for a corner by Twardzik.
Saints had another chance five minutes into the second half as Gary Miller hooked the ball across from the goal-line and Steven MacLean sent his diving header inches wide of the post.
Motherwell responded three minutes later when substitute Fraser Kerr had his header cleared off the line by Miller.
Maclean sent a header straight at Twardzik and at the other end Alan Mannus held a low shot from Thomas in quick succession.
But Motherwell continued to push for an equaliser and Sutton’s goal means they are level on points with third from bottom St Mirren in the Scottish Premiership.