Referee Mike Tumilty harshly sent off visiting defender Steven Anderson after 15 minutes and then banished McInnes from the touchline after he remonstrated with assistant referee Keith Sorbie in the aftermath of Johnny Russell's controversial opener - claiming the United player had scored from an offside position.
Sorbie had an eventful afternoon. It was his intervention that convinced Tumilty to give Anderson a second yellow card for an apparent foul on Swanson. It seemed clear to everyone inside Tannadice that the United winger had gone down easily and television replays backed this up.
St Johnstone performed admirably with 10 men but David Robertson's late second sealed the win for United and allowed them to move five points ahead of Kilmarnock in the race to finish fourth.
Source: PA
Source: PA